Abstracts from Society for Neuroscience (SFN) Washington, D.C. • November 15-19, 2008

36 entries found for : sfn2008

Involvement of the habenula in cognition through its regulatory role upon monoamine and acetylcholine transmissions

Lecourtier L (2008) Involvement of the habenula in cognition through its regulatory role upon monoamine and acetylcholine transmissions. Neuroscience 2008 Abstracts 698.4. Society for Neuroscience, Washington, DC.

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Analysis of inhibitory phase of formalin test: Effects of specific neural lesions

Wiley RG, Moore SA, Kline IV RH (2008) Analysis of inhibitory phase of formalin test: Effects of specific neural lesions. Neuroscience 2008 Abstracts 772.4/MM19. Society for Neuroscience, Washington, DC. Summary: The formalin test has been widely used as a model of persistent pain. The 90 mins of formalin-induced nocifensive responding can be divided into two phases (phase 1, first ~10 mins; phase 2, last ~60 mins) separated by a period of reduced responding (interphase, IP), that has received relatively little attention. Behavioral inhibition during the IP of the formalin test has been associated with electrophysiological evidence of inhibition of dorsal horn nociceptive neurons (Henry et al, Pain, 82:57, 1999), probably due, at least in part, to local spinal mechanisms. Behavioral inhibition during IP has been shown to be enhanced by morphine and suppressed by naloxone. In the present study, we sought to determine the effect of selective depletion of specific dorsal horn interneurons known to be involved in nociception, i.e. neurons expressing NPY1R, GalR1 or MOR, or selective destruction of cerebral noradrenergic neurons or spinal cord projecting 5-HT neurons on formalin-induced nociceptive behavior, with particular attention to IP. Type-selective lesions were produced by lumbar intrathecal injection of NPY-saporin, galanin-saporin or dermorphin-saporin, respectively. Cerebral noradrenergic neurons and spinally projecting 5-HT neurons were destroyed using the immunotoxins, anti-DBH-saporin (intracerebroventricular) or anti-SERT-saporin (lumbar intrathecal), respectively. Partial loss of dorsal horn interneurons expressing NPY1R or GalR1 decreased nocifensive responding during IP and phase 2 of the formalin test, while partial loss of MOR-expressing dorsal horn interneurons increased nocifensive responding during IP and during phase 2. Both antiDBH-sap and antiSERT-sap decreased responding during IP, without effects on either phase 1 or 2. These results suggest that the apparent anti-nociception during IP and phase 2 produced by loss of NPY1R- and GalR1-expressing dorsal horn neurons is due to increased inhibition over excitation/facilitation of nociceptive projection neurons, whereas depletion of MOR-expressing interneurons produces the opposite effect. The apparent enhanced nociception during IP, but not phase I and II, produced by anti-DBH-sap and anti-SERT-sap suggests that these neural systems serve to enhance the excitability of nociceptive projection neurons during the formalin IP. Electrophysiologic and pharmacologic studies of formalin IP in selectively lesioned animals combined with the above behavioral findings may reveal new insights into endogenous modulation of nocifensive motor responses and/or nociception. Related Products: NPY-SAP (Cat. #IT-28), Anti-SERT-SAP (Cat. #IT-23), Galanin-SAP (Cat. #IT-34), Anti-DBH-SAP (Cat. #IT-03), Dermorphin-SAP / MOR-SAP (Cat. #IT-12)

Effect of noradrenergic denervation on cerebral cortex catecholamines in the rat

Flore G, Saba P, Paba S, Gessa G, Pistis M, Devoto P (2008) Effect of noradrenergic denervation on cerebral cortex catecholamines in the rat. Neuroscience 2008 Abstracts 726.3/D6. Society for Neuroscience, Washington, DC.

Summary: Previous studies in rats have indicated that extracellular dopamine (DA) content in cortical areas with scarce or undetectable dopaminergic innervation, such as the occipital (Occ) or parietal cortex, is modestly lower than that present in areas densely innervated such as the medial prefrontal (mPF) cortex, suggesting that extracellular DA may originate, other than from dopaminergic, also from the homogeneously and densely distributed noradrenergic terminals. To further verify such hypothesis cortical noradrenergic neurons were lesioned with the intraventricular injection of the immunotoxin anti-DA-beta-hydroxylase saporin. Extracellular DA and noradrenaline (NA) were measured in the mPF and Occ cortices by microdialysis 15 to 18 days after the lesion when tissue NA content had been reduced by about 95%, with respect to control rats injected with PBS. The lesion reduced extracellular NA in both cortices, but increased extracellular DA in the mPF and Occ cortices. To verify if such increase was due to the impairment of DA uptake into NA terminals, the NA transporter was inhibited with nisoxetine (NIS). While in control rats NIS increased both extracellular NA and DA, in denervated rats it failed to modify extracellular NA and DA in either cortex, confirming that the NA transporter had been inactivated by the lesion. To verify if the lesion modified the output capacity of dopaminergic and noradrenergic neurons, the effect of the alpha2-adrenoreceptor blocker RS 79948 (RS), given alone or in combination with NIS, in control and denervated rats was compared. In control rats, RS increased extracellular NA and DA in both cortices; in combination with nisoxetine RS produced a striking more than tenfold increase in extracellular NA and DA. In lesioned rats RS increased DA levels, failed to modify extracellular NA, while its co-administration with NIS slightly increased NA output. However, after RS plus NIS, extracellular DA was increased by the same extent as after RS alone, indicating that denervation had severely impaired the capacity of neurons to increase DA output after alpha2-adrenoceptor block. The possibility that such neurons might correspond to NA neurons surviving the lesion is discussed.

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Depletion of cholinergic neurons in the nucleus accumbens and its possible involvement in schizophrenic symptomatology

Laplante FP, Dufresne M, Lappi DA, Sullivan RM (2008) Depletion of cholinergic neurons in the nucleus accumbens and its possible involvement in schizophrenic symptomatology. Neuroscience 2008 Abstracts 761.18/FF34. Society for Neuroscience, Washington, DC.

Summary: Schizophrenia is a mental disorder characterized by dysfunctions in several neurotransmitter systems including the central cholinergic system. While alterations in cholinergic neurotransmission have been demonstrated in schizophrenic brains, their biological significance remains to be established. Post-mortem studies of schizophrenic patients have shown a reduction in the density of cholinergic interneurons in the striatum, most prominently in the ventral striatum or nucleus accumbens (N. Acc). Intra-accumbens acetylcholine interacts functionally with the mesolimbic dopaminergic system and is believed to dampen the effects of excessive dopamine (DA) release. Therefore, we hypothesize that a reduction in the density of cholinergic neurons in the N. Acc will be behaviorally relevant, if not causal, to the enhanced (ventral) striatal dopaminergic neurotransmission described in schizophrenia and may contribute substantially to the emergence of schizophrenic symptomatology. In this study we aimed to reproduce in rats a selective reduction in N.Acc. cholinergic cell density, and study the neurophysiological and behavioural consequences of these lesions, relevant to the neuropsychopathology of schizophrenia. A novel saporin immunotoxin coupled with an antibody targeting choline acetyltransferase (ChAT) has been developed. We microinjected this immunotoxin bilaterally (0.5 μg/μl; 0.5 μl) into the N. Acc (core and shell) of adult male Srpague-Dawley rats. Using immunohistochemistry to quantify ChAT staining, we have confirmed that this toxin caused a 40-50 % loss in the number of cholinergic neurons in this region within two weeks post-injection. Lesioned rats exhibited significantly higher spontaneous locomotor activity than control rats and were shown to be hypersensitive to the locomotor activating effects of amphetamine and quinpirole. Furthermore, in separate groups of animals, we have observed in lesioned rats, a reduction in the prepulse inhibition of the acoustic startle response. Taken together, it is proposed that reduction of cholinergic neurons in the N. Acc triggers an enhanced DA responsivity in the N.Acc which may prove highly effective in reproducing behavioral abnormalities analogous to those found in schizophrenia. The neurophysiological consequences of these lesions on DA neurotransmission will be further addressed by measuring both pre- and postsynaptic indices of DA function in this region.

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Lumbar intrathecal CCK-saporin: anatomic and nociceptive effects

Datta S, Chatterjee K, Kline IV RH, Wiley RG (2008) Lumbar intrathecal CCK-saporin: anatomic and nociceptive effects. Neuroscience 2008 Abstracts 773.4/MM32. Society for Neuroscience, Washington, DC.

Summary: Lumbar intrathecal CCK (cholecystokinin) appears anti-opiate in nocifensive reflex testing and may be important in opiate-resistant neuropathic pain states suggesting a role for CCK receptor-expressing dorsal horn neurons in nociception. In the present study, we sought to determine if selective destruction of CCK receptor-expressing superficial dorsal horn neurons alters pain sensitivity or the analgesic potency of morphine using the targeted cytotoxic conjugate (CCK-sap) of CCK to saporin, a ribosome inactivating protein. 28 adult Sprague Dawley rats were injected via lumbar intrathecal catheter with CCK-sap in doses of 500 ng (n=2), 350 ng (n=3), 700 ng (n=3), 1000 ng (n=4), 1500 ng (n=4), or 3000 ng (n=4). Controls included PBS (n=4) or 1500 ng of plain, unconjugated saporin (n=4). 2 weeks later rats were sacrificed. Lumbar spinal cords were frozen sectioned at 40 µm. One-in-six series of transverse sections at L4-6 were immunostained for CCK. Two rats were injected with 1500 ng of CCK-sap followed by transcardiac aldehyde perfusion in 72 hours. L5 Dorsal root ganglia (DRG) sections were stained with cresyl violet and examined for signs of acute cytotoxicity (chromatolysis and karyohexis). 350 to 1500 ng of intrathecal CCK-sap were well tolerated with no obvious signs of any toxicity. 3000 ng of intrathecal saporin led to motor signs within 72 hours including increased muscle tone, leading to tonic hind limbs extension. Subsequently, twelve Long Evans female rats were tested before and after intrathecal injection of either PBS (n=8) or CCK-sap, 1500 ng (n=4) on: 1 - cold plate (15 °C); 2 - thermal preference shuttle box testing (15/45°C); 3 - hotplate at 44°C, 47°C and 52°C and 4 - thermal preference after morphine (0.5, 1 and 2.5 mg/kg s.c). Anatomical analysis revealed that 1500 ng of CCK-sap decreased CCK immunostaining in the L4-6 Dorsal horn. No acute cytotoxicity was seen in the DRG with1500 ng CCK-sap. Intrathecal CCK-sap was well tolerated at doses ≤1500 ng. CCK-sap produced increased hot side time and decreased crossovers in the thermal preference test. In contrast, CCK-sap decreased latency to first hindpaw lift and increased total responding on the 44 °C hotplate. CCK-sap rats also showed increased hot side time at 45° C at all morphine doses (0, 1 and 2.5 mg/kg s.c.) also with decreased crossovers. We interpret these observations to indicate that CCK-sap produced increased nocifensive reflex responding on the 44° C hotplate consistent with positive modulation of motor responsiveness, and CCK-sap reduced aversion to 45° C heat consistent with an analgesic effect that was additive with morphine.

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Interactions between corticosterone and catecholaminergic afferents in the regulation of neuropeptide gene expression in neuroendocrine CRH neurons in the paraventricular nucleus of the hypothalamus

Rapp KL, Watts AG (2008) Interactions between corticosterone and catecholaminergic afferents in the regulation of neuropeptide gene expression in neuroendocrine CRH neurons in the paraventricular nucleus of the hypothalamus. Neuroscience 2008 Abstracts 782.2/RR7. Society for Neuroscience, Washington, DC.

Summary: Neurons in the medial parvicellular part of the paraventricular nucleus of the hypothalamus (PVH) are responsible for neuroendocrine activation of corticotropes in the anterior hypophysis. While corticotropin-releasing hormone (CRH) is the primary peptide responsible for synthesis and release of adrenocorticotropin hormone (ACTH), vasopressin (AVP) is also effective in stimulating ACTH, which stimulates synthesis & secretion of corticosterone (CORT) from the adrenal cortex. This descending pathway, the HPA axis, is part of the stress axis, as its output of CORT facilitates adaptation to changes in energy. While AVP is synthesized in both parvicellular and magnocellular populations of the PVH, it is the AVP in the parvicellular PVH that colocalizes with CRH and increases after adrenalectomy (ADX). The underlying mechanisms contributing to the CORT regulation of Crh and Avp expression still remain elusive, particularly with regard to the role of neural afferents. A major afferent projection system to the PVH originates from hindbrain catecholaminergic (CA) neuron subpopulations. Using saporin-anti-dopamine beta hydroxylase (DSAP) immunotoxin conjugate, to specifically eliminate CA afferents has revealed the importance of CA projections to PVH for both increased Crh expression, and elevated levels of circulating ACTH & CORT following glycemic challenges. We utilized DSAP-mediated deafferentation, followed by ADX and CORT replacement, to determine the role of CA afferents in mediating effects of circulating CORT on Crh and Avp regulation. Male Sprague Dawley rats (~315g) received acute bilateral microinjections of DSAP stereotaxically delivered into the PVH. A control group received bilateral microinjections of saporin conjugated to a non-targeting mouse IgG (SAP). One week later, rats received ADX and timed-release CORT pellet implants (25, 50 or 100 mg). Seven days post-ADX, rats were killed, and radioimmunoassay of plasma from terminal blood samples revealed significantly higher CORT levels in DSAP- vs. SAP-treated rats in CORT replaced groups: 25 mg (p < 0.001), 50 mg (p < 0.01). In contrast, in situ hybridization revealed significantly increased CRH mRNA levels (p < 0.001) and AVP hnRNA levels (p < 0.02) in DSAP- vs. SAP-treated rats with comparable plasma CORT levels. These results suggest that loss of hindbrain CA afferents contributes to the ability of circulating CORT to regulate Crh and Avp expression. The data implicate synergistic interactions between CORT & PVH neural afferents that provide critical metabolic information from the periphery in the regulation of CRH neuroendocrine neurons. Supported by NINDS. (NS029728)

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The retroabducens region is necessary for rapid eye movement (REM) during REM sleep in the rat

Pedersen NP, Anaclet C, Vetrivelan R, Saper CB, Lu J (2008) The retroabducens region is necessary for rapid eye movement (REM) during REM sleep in the rat. Neuroscience 2008 Abstracts 784.15/RR66. Society for Neuroscience, Washington, DC.

Summary: REM sleep is characterized by REMs, atonia of the non-respiratory musculature, and active dreaming during which the electroencephalogram (EEG) is desynchronized in humans and shows increased theta activity in rodents. Surprisingly, the source of the actual REMs during REM sleep is not known, although Pompeiano and Morrison (1965) described the reduction or absence of phasic REM phenomena after electrolytic lesion of the medial and spinal vestibular nuclei in the cat. Using the neurotoxins ibotenic acid and saporin-conjugated anti-orexin B IgG, we systematically placed cell-specific lesions in brainstem candidate structures for the generation of REMs in rats equipped for chronic recording of EEG, electrooculogram, and electromyogram. Lesion of a ‘retroabducens’ area, located immediately caudal and extending ventrally from the abducens nucleus, although leaving the abducens nucleus intact, abolished REMs (as well as waking saccades), without affecting other aspects of REM sleep. Animals with retroabducens lesions showed maintenance of slow oscillations in eye position, characteristic of non-REM or slow wave sleep, throughout REM sleep. Lesions of the medial vestibular nucleus, nucleus prepositus hypoglossi and immediately rostral to abducens did not affect REMs. We hypothesize that the retroabducens area may be required for the generation of saccadic eye movements, similar to the paramedian pontine reticular formation as described in cats and monkeys. The retroabducens region appears to be critical for generating the REMs that characterize REM sleep, but most likely downstream from the REM sleep generator.

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Medullary circuitry regulating trigeminal motor nucleus phasic activity during rapid eye movement sleep in the rat

Anaclet C, Pedersen NP, Lu J (2008) Medullary circuitry regulating trigeminal motor nucleus phasic activity during rapid eye movement sleep in the rat. Neuroscience 2008 Abstracts 784.16/RR67. Society for Neuroscience, Washington, DC.

Summary: Rapid Eye Movement (REM) sleep or paradoxical sleep is characterized by activation of the cortical and hippocampal EEG, atonia of postural muscles (neck and limbs), and phasic movements of cranial muscles (eyes, chin, ears and whiskers). We have previously established that glutamatergic neurons of the sublaterodorsal tegmentual nucleus (SLD) play a critical role in generating postural muscle atonia during REM sleep. It has been further proposed that the SLD produces REM motor atonia by stimulating spinal inhibitory neurons, which in turn inhibit spinal motor output neurons. It is not known however whether the SLD is also involved in the regulation of tonic and phasic events of cranial muscles during REM sleep (e.g., rapid eye movement, phasic masseter activation). Previous studies have shown that the supraolivary medulla (SOM, dorsal to the inferior olive) and parvocellular reticular (PCRt) nucleus in the medullary reticular formation project to relevant cranial motor nuclei, including: the trigeminal motor nucleus (Mo5), retroabducens region, facial nucleus (Mo7) and hypoglossal nucleus (Mo12). It is therefore possible that either the SOM or the PCRt (or both) may also be involved in regulating cranial muscle activity in REM sleep. To identify the cell groups responsible for REM phasic control of cranial motor nuclei, we examined masseter muscle EMG following cell-specific lesions (anti-orexin B IgG-saporin) of the SLD, SOM or PCRt. Following two weeks of surgical recovery, we recorded the EEG, EMG (neck and masseter muscles) and EOG continuously for two days. Control rats showed significant phasic activation of the masseter muscles, in particular during the second half of REM sleep episodes. This phasic bursting pattern was similar to eye movements during REM sleep. Neither SLD nor PCRt lesions altered the phasic activity of the masseter muscles during REM sleep, although, and as previously reported, SLD lesions did produce REM without atonia in postural muscles. By contrast, lesions in the SOM eliminated phasic activation of the masseter muscles during REM and produced myoclonic twitching of neck muscles. These results indicate that the SOM is involved in the induction of phasic REM activity of masseter muscles, likely via activation of Mo5, whereas SOM projections to the spinal cord are involved in suppression of myoclonic activity of postural muscles.

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Contrasting effects of estrogen on memory tasks in young female rats

Saenz CM, Borowski T, De Lacalle S (2008) Contrasting effects of estrogen on memory tasks in young female rats. Neuroscience 2008 Abstracts 794.17/UU7. Society for Neuroscience, Washington, DC.

Summary: Sleep deprivation may lead to behavioral alterations and it has been associated with a hyperalgesic state in human beings and animal models. The tricyclic antidepressant amitriptyline can be used as an analgesic drug in patients and in chronic pain animal models that are not improved with classical analgesics, such as spinal nerve injury induced model of peripheral neuropathy. The pain hypersensitivity following both paradoxical sleep deprivation (PSD) and peripheral nerve injury shares common spinal mechanisms, which involve at least the glutamate receptors and nitric oxide. In this way, we evaluated the effects of amitriptyline pretreatment in the thermal hyperalgesia observed in paradoxical sleep deprived rats. Amitriptyline (10 and 30 mg/Kg) or saline were administered i.p. during 11 days to male Wistar rats (n = 7/group, 250 - 350 g). In the last 3 or 4 days of treatment the animals were submitted to 72 or 96 hours of PSD, respectively, or remained in home cages, being subsequently evaluated for their thermal sensitivity on a hot plate test (52oC or 46oC), 1 or 24 hours after the last drug administration. In order to verify if the results observed in the highest withdrawal latencies were due to a reduction on the locomotor activity rather than an analgesic effect, the number of squares crossed in an open field arena during 5 minutes, subsequently to the hot plate test was counted. The results demonstrated that paw withdrawal latency response to 52oC was significantly lower in paradoxical sleep deprived rats than controls (-37%, p<0.05). This hyperalgesic effect was also detected in animals pre-treated with 10 mg/kg (-41%, p<0.05) or 30 mg/Kg (-53%, p<0.05) of amitriptyline. At the highest dose, both groups presented a higher withdrawal threshold when compared to their respective saline groups (+185%, p<0.05 and +112%, p<0.05; control and sleep deprived rats, respectively). However, in the open field test a decrease in the number of squares crossed in control animals was observed (-52%, p<0.05), but not in sleep deprived rats (-3%, p>0.05). When the animals were allowed to recover for 24h from sleep deprivation, the pre-treatment with amitriptyline (10 mg/Kg) was not able to prevent the hyperalgesic state (-60%, p<0.05). Even with lower thermal stimulus (46oC) and sleep deprivation period (72h), the difference between control and sleep deprived animals could still be detected (-40%, p<0.05), with no changes after an amitriptyline 10 mg/Kg pre-treatment (-43%, p<0.05). Overall, these findings highlight that thermal pain hypersensitivity induced by PSD was not prevented by amitriptyline pre-treatment, as observed in other models of inductive pain.

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Enhanced sensitivity to phencyclidine following cortical cholinergic denervation

Savage ST, Oberg J, Pernold K, Mattsson A (2008) Enhanced sensitivity to phencyclidine following cortical cholinergic denervation. Neuroscience 2008 Abstracts 842.7/X2. Society for Neuroscience, Washington, DC.

Summary: Alterations in cholinergic signaling in the brain have been implicated as a contributing factor in the pathogenesis of schizophrenia. We have recently shown that cholinergic denervation of cortex cerebri by stereotaxic infusion of the immunotoxin 192 IgG-saporin in the nucleus basalis magnocellularis in adult rats, leads to an enhanced sensitivity to amphetamine. Thus, saporin lesioned rats show a marked increase in locomotor activity, as well as a potentiated dopamine release in nucleus accumbens when challenged with amphetamine. We hypothesize that the loss of cortical cholinergic input alters the activity of cortical glutamatergic neurons and in turn, their regulation of subcortical dopamine neurons. We have previously shown that this cortical cholinergic denervation leads to an increased locomotor response to the NMDA receptor antagonist phencyclidine (PCP), suggesting that disruption of cortical cholinergic activity can lead to disturbances of glutamatergic transmission. In current studies we are investigating attention and memory functions of rats with cholinergic denervation of neocortex using the novel object recognition task. Preliminary data from these investigations shows impairment in performance under PCP-challenge in saporin lesioned rats as compared to sham lesioned controls. These results indicate that cortical cholinergic deficits, in addition to leading to a dramatic potentiation of the locomotor response to PCP, can also lead to an enhanced sensitivity to PCP-induced cognitive impairments. Using pharmacological magnetic resonance imaging (MRI) we are investigating possible spatiotemporal differences in brain activation in rats with cortical cholinergic deficits following administration of PCP. Preliminary data have provided indications of a greater activation in cortical areas in saporin lesioned rats as compared to sham lesioned controls following PCP-challenge. Evaluations of possible alterations in social behavior following cortical cholinergic denervation are ongoing. Social interaction will be investigated under normal conditions, as well as after PCP-challenge. Preliminary results from these studies together with our previous results indicate that loss of cortical acetylcholine can lead to alterations in glutamatergic signaling. These observations are compatible with a possible role of cholinergic deficits in schizophrenia, and provide a possible link between different hypotheses of the disorder.

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Stimulus-, circuit- and intracellular-level determinants of MAP kinase and CREB activation in parvicellular hypothalamic paraventricular neurons

Khan AM, Rapp KL, Ponzio TA, Sanchez-Watts G, Watts AG (2008) Stimulus-, circuit- and intracellular-level determinants of MAP kinase and CREB activation in parvicellular hypothalamic paraventricular neurons. Neuroscience 2008 Abstracts 865.23/MM24. Society for Neuroscience, Washington, DC.

Summary: Systemic insulin or 2-deoxyglucose (2-DG) rapidly elevate phosphorylated MAP kinases (phospho-ERK1/2) and/or CRH hnRNA in PVHp neurons, and increase circulating ACTH and corticosterone. These neuroendocrine responses are likely driven by hindbrain-originating catecholaminergic (CA) neuron subpopulations, which richly innervate the PVHp and are activated by glycemic challenges. Supporting this, acute in vivo or in vitro PVH delivery of the prototypical catecholamine, norepinephrine (NE), recapitulates these responses (J Neurosci, 2007, 27:7344-7360). Here, we determined whether PVHp ERK/CREB phosphorylation responses require: 1) intact CA afferents, when triggered by three distinct in vivo challenges; and 2) upstream MEK kinase activity, when triggered by NE application in acute hypothalamic slices maintained in vitro. Methods. Rats given PVH microinjections of anti-dopamine-b-hydroxylase (DBH)-saporin antibody-toxin conjugate (DSAP) or mIgG-saporin control conjugate received either normal 0.9% saline vehicle or one of three systemic challenges: insulin (2 U/kg, i.v.); 2-DG (250 mg/kg, i.v.); or hypertonic saline (1.5 M, i.p.) and sacrificed 30 min later. Brains were processed for CRH mRNA/hnRNA hybridization, or DBH, phospho-ERK or phospho-CREB immunocytochemistry. Plasma was collected for hormone determinations at 0 and 30 min. In separate in vitro studies, acute hypothalamic slices received either no treatment (controls), or received bath-applied NE (100 mM) in the presence or absence of the MEK inhibitor, U0126 (10 mM), or the inactive MEK inhibitor analogue, U0124 (10 mM). Ten min later, slices were placed in fixative. Results. 1. Sham-lesioned animals: Relative to vehicle, all challenges elevated phospho-ERK1/2, phospho-CREB, and ACTH/corticosterone levels; and, except for insulin, also increased CRH hnRNA. 2. Lesioned animals: DSAP treatment selectively destroyed hindbrain-originating CA afferents. In insulin- and, to a lesser extent, 2-DG-treated animals, this loss was accompanied by markedly reduced PVH phospho-ERK1/2 and circulating ACTH/corticosterone. In contrast, these responses remained robust in CA-deafferented hypertonic saline-treated rats. Phospho-CREB levels were differentially reduced relative to phospho-ERK in lesioned rats. 3. Slices: NE-induced PVH elevations of phosphorylated ERK1/2 and CREB were reduced markedly by U0126, but not U0124, pre-treatment. Conclusions. PVHp phospho-ERK selectively couples to CA afferents during glycemic challenges and ERK/CREB recruitment appears to require MEK activity.

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Ventrolateral periaquaductal gray (vlPAG): Key area for REM sleep propensity

Thankachan S, Kaur S, Blanco-Centurion C, Sakurai T, Yanagisawa M, Shiromani PJ (2008) Ventrolateral periaquaductal gray (vlPAG): Key area for REM sleep propensity. Neuroscience 2008 Abstracts 586.3/SS36. Society for Neuroscience, Washington, DC.

Summary: In an effort to determine how loss of hypocretin/orexin (HOX) increases REM sleep we have used the neurotoxin, hypocretin-2-saporin (HCRT2-SAP), to lesion HOX receptor bearing neurons. Our efforts have focused on the pons (Blanco-Centurion et al., EJN 19:2741, 2004) since REM sleep is generated from there. Here, we investigate the vlPAG, a region where muscimol robustly increases REM sleep in cats (Sastre et al., Neuroscience, 74:415, 1996), and where HOX might activate GABA neurons that inhibit REM sleep. Lesion of vlPAG neurons with HCRT2-SAP should increase REM sleep. HCRT2-SAP (16.5ng/23nl) or saline (23nl; 0.9%) was injected (glass pipette; isofluorane anesthesia) to the vlPAG area in hypocretin/orexin null mice (HOX null) and in GAD-GFP mice [TgN(GadGFP)45704Swn; to visualize the GABA neurons]. Sleep was recorded 15th and 16th days after the lesion (12:12LD cycle). vlPAG lesion (n=5) significantly (+48.19%) increased REM sleep at night in HOX null mice compared to saline treated HOX null mice (n=7); REM sleep during the day was not changed. Over the 24h period REM sleep was significantly increased (+18.78%). However, cataplexy did not increase. In the GAD-GFP mice vlPAG lesions (n=8) also significantly increased REM sleep at night (+79.4%) compared to saline controls (n=8). The vlPAG lesions caused a significant increase in the number of short bouts (<40sec) of wake, NREM and REM sleep during both day and night. HOX null mice already have highly fragmented sleep, and increased REM sleep at night. Since vlPAG lesions produced a greater sleep fragmentation and increased REM sleep even further suggests that the vlPAG represents a key area, downstream of HOX neurons, in gating REM sleep propensity.

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The substantia nigra and the control of sleep

Lai YY, Hsieh KC, Nguyen D, Siegel JM (2008) The substantia nigra and the control of sleep. Neuroscience 2008 Abstracts 586.9/SS42. Society for Neuroscience, Washington, DC.

Summary: It has been established that the substantia nigra (SN) is involved in the control of motor activity. However, its role in the regulation of sleep remains unclear. We have previously found that NMDA lesions in the SN suppress sleep in the cat. A recent study demonstrated that lesions of the SN by hypocretin2-saporin result in severe insomnia in the rat. Thus, we hypothesized that activation of the SN by application of either excitatory transmitter analogs/agonists or GABA receptor blockers would induce sleep. Hypocretin had been reported to exert an excitatory effect on SN neuronal activity. The SN receives dense projections from hypocretin neurons. In the current study, we investigated whether microinfusion of hypocretin into the SN would modulate sleep and wakefulness in freely moving rats. Adult male Sprague-Dawley rats were implanted with EEG and EMG electrodes, and a guide cannula targeting the SN. Experiments were conducted one week after the rat had been implanted. The rats were housed individually in sound-attenuated chambers in LD 12:12. Hypocretin-1 was delivered via microdialysis probes (CMA/11) at a rate of 2 μL/min. Each one-hour of hypocretin infusion (ZT4 to ZT5 in the light period) was preceded by a 2-hour baseline period of artificial cerebrospinal fluid (aCSF) infusion and was followed by a 2-hour aCSF infusion. The lower concentration of hypocretin-1 (36 μM, n=2) reduced wakefulness by 19% ± 9.5% and increased slow wave sleep (SWS) by 12.8% ± 2.3% of the baseline level. The higher concentration of hypocretin-1 (72 μM, n=3) reduced wakefulness by 30.5% ± 16.4% of the baseline level and produced an increase in both SWS and REM sleep, by 10.2% ± 2.2% and 63.7% ± 26.6% respectively. The increased sleep induced by both concentrations of hypocretin were also observed in the first post-infusion hour. In conclusion, we found that hypocretin-1 has a sleep-promoting effect in the SN. Our previous study showed that hypocretin (orexin) neurodegeneration occurred in Parkinson’s disease patients. This finding suggests that sleep difficulties in Parkinson's disease patients may result from a combination of lesions in the SN and the secondary effects of the loss of hypocretin neurons.

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Effects of lesions of three downstream targets of orexin/hypocretin neurons does not support the “flip-flop switch” model

Blanco-Centurion CA, Shiromani PJ (2008) Effects of lesions of three downstream targets of orexin/hypocretin neurons does not support the “flip-flop switch” model. Neuroscience 2008 Abstracts 586.2/SS35. Society for Neuroscience, Washington, DC.

Summary: Hypocretin (HCRT) neurons heavily innervate the cholinergic neurons in the basal forebrain (BF), histamine neurons in the tuberomammillary nucleus (TMN) and the noradrenergic locus coeruleus (LC) neurons, three populations that have traditionally been implicated in arousal. Based on the innervation HCRT neurons may regulate arousal by driving these downstream arousal neurons. Here we directly test this hypothesis by simultaneously lesioning these neurons using three saporin-conjugated neurotoxins. Forty four adult male Sprague-Dawley rats received stereotaxically (under anesthesia) delivered microinjections of three different saporin-conjugated neurotoxins as follows: HCRT2-saporin (250 ng/L in 0.25 µL) to lesion TMN neurons; anti-DBH-saporin (1 μg/μL in 0.25 μL) to destroy noradrenergic LC neurons; and 192-IgG-saporin (2 μg/μL ICV; 3μL) to kill the BF cholinergic neurons. Control rats were injected with pyrogen-free saline solution. Rats that had triple lesion the neuronal loss was as follows: -89.2% of ChAT-BF, -75.4% of ADA-TMN and -93.3% of DBH-LC). Surprisingly, in these rats three weeks after lesion the daily levels of wake were not changed. However, rats with lesions of two (ChAT+LC) or three (Chat+TMN+LC) neuronal populations had fewer arousals (<40sec) and a more stable sleep architecture (fewer transitions between states) compared to non-lesioned saline rats. These results are contrary to predictions of the “flip-flop” model. From these data and evidence from knockout mice, we hypothesize that the LC, histamine TMN, and BF cholinergic neurons serve to rapidly awaken a sleeping brain, and with it turn on cognitive function, attention, vigilance, and if necessary the “flight-or-fight” response. Hyperactivity of these neurons may underlie the hyperarousal in PTSD.

Related Products: Orexin-B-SAP (Cat. #IT-20)

Effects of cholinergic deafferentation of medial, prefrontal cortex on a cross-modal divided attention task

Carter ES, Newman LA, Galler JR, Mcgaughy J (2008) Effects of cholinergic deafferentation of medial, prefrontal cortex on a cross-modal divided attention task. Neuroscience 2008 Abstracts 590.6/TT58. Society for Neuroscience, Washington, DC.

Summary: Previous research has shown that cholinergic lesions of the nucleus basalis magnocellularis impair cross-modal divided attention (Turchi and Sarter 1997). Cholinergically lesioned rats showed increased response latencies relative to sham-lesioned rats if required to divide attention but did not differ from sham-lesioned rats when tested in a focused attention condition. In the present study, the effects of selective cholinergic depletion of the medial, prefrontal cortex were assessed in the same cross-modal divided attention task (CMDAT). Male, Long-Evans rats were trained on one set of conditional response rules for visual stimuli and another for auditory stimuli. In the CMDAT, rats received 20 trials of either auditory or visual stimuli followed by twenty trials of the alternate modality (focused attention). Within the same session rats received 60 trials of a randomized sequence of all possible stimuli (divided attention). These trials were followed by two additional blocks of focused attention (20 trials/block) so the trial block sequence was Focused Attention 1 (FA1): Divided Attention (DA) : Focused attention 2 (FA2). Subjects received infusions of 192 IgG saporin (pACh-LX) or its vehicle (SHAM-LX) to the prelimbic cortex. Response latencies for all subjects were longer under conditions of divided attention when performance was compared to the first block of focused attention trials. However in pACh-LX rats response latencies in the second block of focused attention trials were longer than in the divided attention trials. The slowed performance in the FA2 block may suggest cognitive fatigue after performing the divided attention trials or may be due to the effects of prolonged time on task. To address this question, a novel sequence of trials DA : FA1 : FA2 was tested. This session showed no difference in response latencies across blocks in either group. The lack of increased response latencies in FA2 suggests the effect in the standard task is related to cognitive fatigue after completion of the DA block and prolonged time on task. The accuracy of pACh-LX rats was decreased in the divided attention block relative to SHAM-LX rats in this block and relative to pACh-LX rats’ own performance in the DA block of the standard task. This loss of accuracy with decreased latency suggests that lesioned rats show a cost of divided attention if no focused attention blocks precede divided attention testing. These data support the hypothesis that cholinergic afferents to the prefrontal cortex mediate divided attention and a loss of these afferents exacerbates cognitive fatigue.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Selective cholinergic lesions of the nucleus basalis magnocellularis disrupt attention in appetitive trace conditioning

Butt AE, Kinney-Hurd BL, Flesher MM, Amodeo DA, Horn LR, Greenfield V, Lladones R, Hernandez G, Loson L (2008) Selective cholinergic lesions of the nucleus basalis magnocellularis disrupt attention in appetitive trace conditioning. Neuroscience 2008 Abstracts 686.14/SS65. Society for Neuroscience, Washington, DC.

Summary: Pavlovian trace conditioning, but not delay conditioning, is a form of declarative memory that requires attention and depends on the medial prefrontal cortex and hippocampus. We have previously shown that selective lesions of the cholinergic basal forebrain projections to the neocortex and to hippocampus disrupt trace conditioning but not delay conditioning. The current experiment examines the contribution of the cortical cholinergic projections of the nucleus basalis magnocellularis (NBM) to the behavioral impairments previously observed following complete basal forebrain lesions involving both the NBM and the hippocampally-projecting medial septum (MS). We hypothesized that selective lesions of the cholinergic NBM neurons would disrupt trace conditioning in a manner similar to that observed following basal forebrain lesions. Additionally, because cholinergic modulation of prefrontal cortex mediates attention in other tasks, we hypothesized that increasing demands on attention in trace conditioning would exacerbate NBM lesion-induced impairments. Rats with bilateral 192 IgG-saporin lesions of the NBM and sham lesion control animals were tested in the trace conditioning paradigm either in the presence or absence of an attention-demanding visual distractor (intermittent, unpredictable flashing light). Rats received 60 trials per day for 10 days, where each trial consisted of a 10 s white noise CS, followed 10 s later by the delivery of a sucrose pellet unconditioned stimulus (US). Conditioned responding was assessed by measuring approach to the food cup. Approach during the CS itself was considered to be non-adaptive, while approach during the trace interval was classified as adaptive responding. Contrary to our hypothesis, results showed that NBM lesions failed to impair acquisition of trace conditioning in the absence of additional attentional demands. These findings suggest that the trace conditioning impairment previously observed following complete basal forebrain lesions were due either to damage to the hippocampally-projecting MS or to a cumulative effect of combined NBM and MS damage. The presence of the visual distractor, however, disrupted acquisition performance in the current experiment as hypothesized. The NBM lesion group in the distracted condition showed excessive non-adaptive responding during CS presentation as compared to controls. The increased attentional load caused by the visual distractor appears to have caused a disinhibition of non-adaptive responding in the NBM lesion group. These results suggest that cholinergic modulation of neocortex is involved in mediating attention during trace conditioning.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Protection from dendritic atrophy with testosterone following partial motoneuron depletion: Timing and duration of treatment, functional correlates in motor activation

Coons KD, Sengelaub DR (2008) Protection from dendritic atrophy with testosterone following partial motoneuron depletion: Timing and duration of treatment, functional correlates in motor activation. Neuroscience 2008 Abstracts 556.23/CC10. Society for Neuroscience, Washington, DC.

Summary: We have previously demonstrated that partial depletion of motoneurons innervating the quadriceps muscles induces dendritic atrophy in remaining motoneurons; this atrophy can be attenuated in a dose-dependent fashion, and in both male and female rats, with testosterone (T) treatment. In the present study, we examined (1) how the timing and duration of T treatment affect its ability to attenuate induced atrophy in remaining quadriceps motoneurons, and (2) the effects of induced atrophy and T treatment on subsequent motor function in male rats. Motoneurons innervating the vastus medialis muscles were selectively killed by intramuscular injection of cholera toxin-conjugated saporin. Rats were then treated with supplemental T at different times post-saporin injection (immediately, or at 2 or 3 weeks), or for different durations (1, 2, 3, or 4 weeks) or left untreated. All T treatments consisted of subcutaneous implants designed to produce plasma titers in the normal physiological range. Following treatment, the morphology of motoneurons innervating the ipsilateral vastus lateralis muscles was examined using retrograde labeling with cholera toxin-conjugated HRP. In a separate set of rats, quadriceps motoneuron activation was assessed using peripheral nerve recording. Motoneuron morphology and motor activation were also assessed in a group of untreated normal males. Partial motoneuron depletion resulted in dendritic atrophy in remaining quadriceps motoneurons. Treatment with T attenuated this atrophy, but in a time-sensitive manner. Four weeks of T treatment (delivered immediately post-saporin), or two weeks of T treatment (after a delay of two weeks post-saporin) were both effective in attenuating induced dendritic atrophy. However, dendritic atrophy in animals with immediate T treatment of shorter durations or longer delays in the start of treatment was comparable to that of animals who received no supplemental T. Consistent with the morphological changes, partial motoneuron depletion in otherwise untreated males resulted in deficits in motor activation: activation of quadriceps motoneurons required greater stimulus intensities and resulted in decreased amplitudes of motor nerve activity. Importantly, just as observed for dendritic morphology, these changes were attenuated by treatment with supplemental T. These results demonstrate that the neuroprotective effect of T on motoneuron morphology is more dependent on the timing of treatment than on its duration, and also provide a functional correlate of the morphological effects of that treatment, further supporting a role for T as a neurotherapeutic agent in the injured nervous system.

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Changes in energy metabolism after ventrolateral preoptic lesions in rats

Ramalingam V, Fuller PM, Lu J, Saper CB (2008) Changes in energy metabolism after ventrolateral preoptic lesions in rats. Neuroscience 2008 Abstracts 586.14/SS47. Society for Neuroscience, Washington, DC.

Summary: The ventrolateral preoptic area (VLPO) is critically involved in the regulation of sleep. For example, lesions of the VLPO have been reported to cause profound insomnia and sleep fragmentation in rats. We evaluated possible changes in energy metabolism and motor behaviors secondary to chronic sleep restriction in VLPO lesioned rats. Under anesthesia (chloralhydrate, 350 mg/kg, i.p.), adult male Sprague Dawley rats (n = 17) received stereotaxic injections of orexin-saporin into the VLPO and were also implanted with EEG/EMG electrodes to assess sleep-wakefulness. Food, water, and body mass measurements were collected for 60 post-lesion days. Sleep-wakefulness was recorded on post-lesion Days 20 and 50. On post-lesion Day 60, the animals were deeply anesthetized and transcardially perfused with 10% formaldehyde. The brains were removed and processed for histological verification of the lesion site. VLPO lesions produced a decrease (34%) in non rapid eye movement sleep (NREM) and a decrease in NREM sleep bout duration (115 ± 5 sec in the VLPO lesioned rats Vs 133 ± 2 in control rats, P < 0.01). The VLPO lesioned animals also exhibited increased food intake when compared to the age-matched controls (0.45 ± 0.004 grams per gram of lean body mass Vs 0.39 ± 0.01 grams per gram of lean body mass, P = 0.05). Food intake (r = 0.90, P<0.001), but not water intake was positively correlated with the amount of sleep loss. Although the weight gain in the VLPO lesioned rats was not statistically different from the controls, it was negatively correlated with the amount of sleep loss in those animals (r = 0.51, P = 0.05). Although the VLPO lesioned animals balanced on the rotatrod for 25% less time than the controls, this did not reach statistical significance, perhaps because the variance was so high in both groups (87 ± 23 seconds Vs 116 ± 25 sec in control rats, P>0.05). The close correlation of sleep loss with changes in food intake and body weight after the VLPO lesions suggests that the increased feeding but lower body weight may be due to the sleep loss, rather than a consequence of damaging neurons adjacent to the VLPO, which would not correlate with sleep loss.

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Cholinergic deafferentation of the neocortex with 192 IgG-Saporin impairs feature binding in rats

Botly LC, De Rosa E (2008) Cholinergic deafferentation of the neocortex with 192 IgG-Saporin impairs feature binding in rats. Neuroscience 2008 Abstracts 418.2. Society for Neuroscience, Washington, DC.

Summary: The binding problem refers to the fundamental challenge of the central nervous system to integrate sensory information registered by distinct brain regions to form a unified neural representation of a stimulus. While the cognitive mechanisms and functional neuroanatomy of feature binding have been well examined by the human cognitive literature, the neurochemistry of feature binding remains unknown. We contend that acetylcholine (ACh) is critical for feature binding given this neuromodulator’s presumed role in modulating attention, and the well-established importance of attention to feature binding. Using systemic pharmacology in rats, we have previously established a critical role for ACh in feature binding at encoding, but have yet to identify the target brain regions cholinergic input must reach for successful feature binding to occur. Given the recognized importance of the frontal and parietal cortices to attentional processing, we hypothesized that cholinergic deafferentation of the neocortex would impair feature binding in a similar manner to that of systemic cholinergic blockade. To test this hypothesis, rats received bilateral 192 IgG-Saporin lesions of the nucleus basalis magnocellularis (NBM) of the basal forebrain. Relative to sham-lesioned rats, NBM-lesioned rats were significantly impaired at acquiring a crossmodal Feature-Conjunction (FC) task, while their ability to retrieve the FC task and to acquire a crossmodal Feature-Singleton (FS) task remained intact. These findings provide further support for our cholinergic attentional hypothesis of feature binding and reveal the importance of neocortical cholinergic input from the basal forebrain to the feature binding encoding process.

Related Products: 192-IgG-SAP (Cat. #IT-01)

The effect of electrical stimulation in the rats for dementia animal model.

Jeong D, Hwang Y, Chang J (2008) The effect of electrical stimulation in the rats for dementia animal model. Neuroscience 2008 Abstracts 340.11/M2. Society for Neuroscience, Washington, DC.

Summary: Forebrain Cholinergic neurons in the nucleus basalis meynert (NBM) project primarily to the neocortex, and those in the medial septum project to the hippocampus and make a role in memory function. A case study was reported that electrical stimulation of the hypothalamus improves hippocampus dependent memory function. The hypothesis of this study is that electrical stimulation of NBM would induce memory enhancement by effect on neocortex and/or hippocampus. Animal models were induced by selective immunolesion of cholinergic neurons. The cholinergic immunotoxin 192 IgG-saporin was injected in lateral ventricle. 192 IgG-saporin injected rats were compared with Dulbecco’s phosphate bufferd saline (DPBS) injected rats. Neurological deficit and functional outcome were determined by immuohistochemistry using anti-choline acetyl transferase antibody and Morris water maze behavioral test. DBS electrode was implanted in NBM and Stimulation parameters are selected from animal stimulation test. Extent of the cholinergic lesion was showed in the basal forebrain complex region at 192 IgG-saporin injected rats. 192 IgG-saporin injected rats were severely impaired in the probe test of the water maze test. We observe that NBM stimulation induced memory enhancement in dementia models through the behavioral test. Therefore, our animal DBS system could be a useful instrument for investigation of dementia.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Intra cisterna magna and Rostral ventromedial medulla injection of anti-Serotonin transporter-Saporinpertussis enhanced somatotopically different c-Fos expression and pain related behaviour in the medullary dorsal horn in rats

Sugiyo S, Uehashi D, Masawaki A, Ohyamaguchi A, Abe T, Yonehara N, Takemura M (2008) Intra cisterna magna and Rostral ventromedial medulla injection of anti-Serotonin transporter-Saporinpertussis enhanced somatotopically different c-Fos expression and pain related behaviour in the medullary dorsal horn in rats. Neuroscience 2008 Abstracts 369.11/KK23. Society for Neuroscience, Washington, DC.

Summary: The rostral ventromedial medulla (RVM) is a key center in descending pain modulator, which contain serotonergic neurons having descending projectional terminals in the trigeminal caudal nucleus (Vc; medullary dorsal horn). The functional significance of serotonergic neurons in the RVM is largely unknown. Pretreatment with anti IgG serotonin transporter conjugated with neurotoxin, saporin (anti-SERT-SAP; Advanced Targeting Systems) selectively eliminates cells bearing serotonin transporter, namely serotonergic neurons. 2-4 weeks after injection of anti-SERT-SAP (0.5 µM, 10 nl) into the RVM, the number of serotonin-immunoreactive (IR) cells in the RVM significantly decreased. Formalin injection (1,25% in saline) into the upper lip induced biphasic nociceptive pain-related behavior (PRB). In the rats anti-SERT-SAP-pretreated into the RVM, showed decreased the number of formalin-induced PRB at 1st and 2nd phase compared with the Blank-SAP-pretreated control. 2-4 weeks after intra cisterna magna (CM) pretreatment of anti-SERT-SAP(5 µM, 5 µl), the number of serotonin-IR cells in the RVM also reduced. In stark contrast to the results of pretreatment into the RVM, anti-SERT-SAP-pretreated rats into the CM increased the number of formalin-induced PRB at 1st and 2nd phase. These results indicate that serotonergic neurons in the RVM are constituted by two groups, 1) having pronociceptive function and 2) antinociceptive function projecting to the superficial layers of the Vc.

Related Products: Anti-SERT-SAP (Cat. #IT-23)

Selective lesion of retrotrapezoid Phox2b-expressing neurons attenuates the central chemoreflex in rats

Moreira TS, Takakura AC, Stornetta RL, Guyenet PG (2008) Selective lesion of retrotrapezoid Phox2b-expressing neurons attenuates the central chemoreflex in rats. Neuroscience 2008 Abstracts 383.3/RR70. Society for Neuroscience, Washington, DC.

Summary: Injection of the neurotoxin saporin-substance P (SSP-SAP) into the retrotrapezoid nucleus (RTN) attenuates the central chemoreflex in rats. Here we ask whether these deficits are caused by the destruction of a type of pH-sensitive interneuron that expresses the transcription factor Phox2b and is non-catecholaminergic (Phox2b+TH-). We show that RTN contains around 2100 Phox2b+TH- cells. Injections of SSP-SAP into RTN destroyed Phox2b+TH- neurons but spared facial motoneurons, catecholaminergic and serotonergic neurons and the ventral respiratory column caudal to the facial motor nucleus. Two weeks after SSP-SAP, the apneic threshold measured under anesthesia was unchanged when fewer than 57% of the Phox2b+TH- neurons were destroyed. However, destruction of 70 ± 3.5 % of these cells was associated with a large rise of the apneic threshold (from 5.6 to 7.9% end-expiratory pCO2). In anesthetized rats with unilateral lesions of around 70% of the Phox2b+TH- neurons, acute inhibition of the contralateral intact RTN with muscimol instantly eliminated phrenic nerve discharge (PND) but normal PND could usually be elicited by strong peripheral chemoreceptor stimulation (8/12 rats). Muscimol had no effect in rats with an intact contralateral RTN. In conclusion, the destruction of the Phox2b+TH- neurons is a plausible cause of the respiratory deficits caused by injection of SSP-SAP into RTN. At least 70% of these cells must be killed to cause a severe attenuation of the central chemoreflex under anesthesia. The loss of an even greater percentage of these cells would presumably be required to produce significant breathing deficits in the awake state.

Related Products: SSP-SAP (Cat. #IT-11)

Chemoresponsiveness of the hypothalamic paraventricular nucleus (PVN) is influenced by neuropeptide Y

Mack SO, Wu M, Xu G (2008) Chemoresponsiveness of the hypothalamic paraventricular nucleus (PVN) is influenced by neuropeptide Y. Neuroscience 2008 Abstracts 383.7/RR74. Society for Neuroscience, Washington, DC.

Summary: The hypothalamic paraventricular nucleus (PVN) initiates autonomic responses to stress and behavioral changes. Neuropeptide Y-containing neurons primarily from the arcuate nucleus and, to a lesser extent, from the brainstem innervate preautonomic oxytocin-containing neurons in the PVN. The role of the PVN in mediating the effects of NPY on energy balance has been studied extensively; however, whether NPY influences respiratory drive via the PVN is not known. Previously, we demonstrated that stimulation of the PVN modulates cardiorespiratory responses via oxytocinergic innervation of neurons in the rostral ventrolateral region of the medulla oblongata where rhythm generating neurons are located. In this study, we selectively lesioned neurons in the PVN bilaterally with neurotoxin neuropeptide Y-saporin (NPY-SAP; 50 ng/100 μl per side) or blank-saporin (control vehicle). Both groups of rats showed similar (P>0.05) increases in body weight gain and intake of food and water over an 8 week period after lesioning. Core body temperature, measured at the same time every day, was also similar for both groups (P>0.05). At 4 weeks post lesioning, NPY-SAP treatment had no effect (P>0.05) on respiratory frequency (fR), tidal volume (VT) and minute ventilation (VE ) in awake, unrestrained animals breathing room air. During exposure to a hypercapnic challenge (5% CO2) for 10 minutes, fR (135 ± 7 vs 114 ±5 breaths min-1) and VE (154 ±13 vs 114± 5 ml min-1 100g-1 ) for the treated animals were significantly elevated (P<0.05) above responses for the control rats. Tidal volume for the treated (1.1 ±0.06) and the control (1.0 ± 0.03) groups was not different (P>0.05). Sensitivity to CO2 with respect to fR in the treated animals reached a peak at 4 weeks and declined thereafter over the next 4 weeks. While there were no apparent changes in morphology or number of parvocellular oxytocin-containing neurons 4 weeks after lesioning, abnormal morphology and a significant (P<0.05) reduction in oxytocin immunoreactive cells were prominent by 8 weeks post treatment. These findings indicate that NPY plays a role in modulating the respiratory response to hypercapnic stress through oxytocin neurons in the PVN. Further studies are needed to determine whether alterations in this pathway may be involved in the onset of hypoventilation associated with obesity.

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Unilateral lesions of lateral hypothalamic orexin neurons impair surprise-induced enhancements of learning

Holland PC, Angeli N, Lasseter H, Wheeler DS (2008) Unilateral lesions of lateral hypothalamic orexin neurons impair surprise-induced enhancements of learning. Neuroscience 2008 Abstracts 387.16/SS63. Society for Neuroscience, Washington, DC.

Summary: Recent evidence indicates that hypothalamic orexin (hypocretin) neurons are importantly involved in arousal, aspects of learned motivational function, and the cholinergic mediation of sustained attention and the enhanced detection of weak but significant cues. Here we examined the role of these neurons in the modulation of attention in the associative learning of rats. The surprising omission of an expected event can enhance attention to cues present at the time of surprise, and hence facilitate subsequent learning about those cues. In previous research, we showed that circuitry including the amygdala central nucleus (CeA), the substantia nigra pars compacta, cholinergic neurons in the substantia innominata/nucleus basalis, and portions of the medial prefrontal and posterior parietal cortex, form a network essential for this surprise-enhanced learning. In the present study, rats received orexin-saporin lesions of the lateral hypothalamus (LH) in one hemisphere and ibotenic acid lesions of CeA in the other. Because most projections between LH and CeA are ipsilateral, this combination of lesions functionally disconnects CeA from LH orexin neurons. Rats in three control groups received unilateral lesions of LH or CeA (with sham lesions of the other region) or sham lesions of both regions. The rats were then trained in a task in which attention was manipulated by shifting a predictive relation between two cues. First, all rats received serial light-tone pairings, half of which were followed by food. Next, for half of the rats in each lesion condition the tone was omitted on nonreinforced trials, whereas the remaining rats continued to receive the same light-tone trials as before. Finally, attention to the light was assessed by measuring the rate of learning a new light-food relation. If the rats were surprised by the omission of tone during the previous phase, then attention to the light would be enhanced, resulting in faster acquisition of light-food conditioning. Consistent with previous findings, sham-lesioned rats and rats with unilateral CeA lesions showed this surprise-induced enhancement. By contrast, rats with unilateral LH lesions showed no such enhancement of learning, but otherwise performed comparably to controls. Notably, damage to CeA contralateral to the LH damage produced no additional impairment. Thus, LH orexin neurons play an important role in the surprise-induced enhancement of attention and learning, but not solely by their interactions with CeA.

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A synergistic role for GABAergic and cholinergic neurons of the medial septum in spatial reference memory processing: assessment with the Morris water-maze and a novel double-H maze in rats

Lecourtier L, Leroux E, Cosquer B, Cassel JC (2008) A synergistic role for GABAergic and cholinergic neurons of the medial septum in spatial reference memory processing: assessment with the Morris water-maze and a novel double-H maze in rats. Neuroscience 2008 Abstracts 389.10/TT38. Society for Neuroscience, Washington, DC.

Summary: The medial septum - from which GABAergic and cholinergic neurons project to the hippocampus - might be one of the key structures involved in hippocampal-dependent spatial memory processing. Indeed, lidocaine-induced septal inactivation disrupts encoding and retrieval, but not consolidation of a spatial memory in the water maze. Furthermore, the activation of septal 5-HT1A receptors prevents encoding but neither immediate consolidation nor retrieval of such a memory. As i) 5-HT1A receptors are located on most GABAergic and a significant part of cholinergic neurons of the medial septum, and ii) highly selective cholinergic lesions in the medial septum weakly affect spatial learning, it is possible that normal spatial memory processing depends on a cooperation between cholinergic and GABAergic neurons of this region. To address this possibility using selective lesions, 192 IgG-Saporine (IgG group) or Orexine-Saporine (OREX group) was infused into the septum to damage cholinergic or GABAergic neurons, respectively. In a third group (IgG/OREX group), both lesions were combined. Sham-operated rats were used as controls. The lesion effects were assessed on locomotor activity and on acquisition/retrieval of two water-maze tasks, the Morris maze and the double-H maze. In separate groups, retrieval was tested at three post-acquisition intervals in the Morris maze, namely 1, 5 and 25 days, and two post-acquisition periods in the double H maze, namely 5 and 25 days. Only the combined lesion resulted in nocturnal hyperactivity. In the Morris water-maze, at 25 days, there was no retrieval, whatever the group; whereas at the 1-day delay all groups retrieved the platform, at the 5-day delay, IgG and OREX rats showed normal performance while IgG/OREX rats were impaired. In the double-H maze, at the 5-day delay all groups remembered the platform location. These effects will be compared to those found at the 25-day delay (experiment currently running). Our data show that the GABAergic and cholinergic neurons of the septum synergistically contribute to the regulation of hippocampal-dependent (declarative-like) spatial memory processing.

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Learning strategy selection in the water maze in medial septal electrolytic and selective cholinergic neurons lesioned rats

Burjanadze M, Beselia G, Chkhikvishvili N, Kotaria N (2008) Learning strategy selection in the water maze in medial septal electrolytic and selective cholinergic neurons lesioned rats. Neuroscience 2008 Abstracts 389.5/TT33. Society for Neuroscience, Washington, DC.

Summary: In this experiment the ability of medial septal electrolytic, selective ACh lesioned (by immunotoxin 192 IgG-saporin) and sham-operated rats, to learn the location of a visible, as well as submerged platform in a water maze was investigated. A total of 36 male outbred albino rats were used in the study. All experiments were approved by the Animal Care and Use Committee of the Institute and were in accordance with the principles of laboratory animal care. The rats’ responses in the competition test were classified as either cue or place directed, based on the swim path for those trials. Sham-operated rats acquired both the visible and hidden platform versions of the task, but when required to choose between the spatial location they had learned and the visible platform in a new location, majority of them swam first to the old spatial location. The medial septal electrolytic lesioned rats acquired the visible platform version of the water maze task but failed to learn the platform location in space. When the visible platform was moved to a new location they often swam directly to it. The medial septal selective ACh lesioned rats, as well as sham-operated, acquired the platform location in space. Sham-operated and selective ACh lesioned rats identified as place responders, had significantly more accurate searches during hidden platform training, providing additional evidence of their effective use of a place learning strategy rather than medial septal electrolytic lesioned rats. These findings suggest that the septo-hippocampal system is essential for accurate spatial learning and suggest its role in processing information about the spatial environment, but deficits observed after septal electrolytic lesions cannot be accounted solely to the loss of hippocampal ACh and raised the unexpected possibility that hippocampal ACh is not essential for all types of hippocampal-dependent memory.

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Galanthamine does not attenuate attentional or temporal impairments subsequent to cholinergic deafferentation of the cortex or hippocampus

Martin MM, Weathered SL, Wagner SJ, Wallace DG (2008) Galanthamine does not attenuate attentional or temporal impairments subsequent to cholinergic deafferentation of the cortex or hippocampus. Neuroscience 2008 Abstracts 441.12/T4. Society for Neuroscience, Washington, DC.

Summary: The role of the basal forebrain cholinergic system in early symptomology of dementia of the Alzheimer’s type (DAT) remains an area of intense debate. Although involvement of the basalocortical cholinergic system in attentional processing has been established, function of the septohippocampal cholinergic system remains to be determined. A recent study demonstrated a double dissociation between these systems in the organization of rat food protection behavior that may parallel the attentional impairments and temporal disorientation observed during the early stages of DAT. The current study sought to examine whether an acetylcholinesterase inhibitor currently used for the treatment of DAT (i.e., galanthamine) could attenuate these deficits. Consistent with previous research, intraparenchymal injections of 192 IgG-Saporin into the nucleus basalis or medial septum area in female Long Evans rats produced dissociable effects on the organization of food protection behavior. Specifically, nucleus basalis lesions selectively reduced the number of successful food protection behaviors; whereas, medial septum lesions selectively disrupted the temporal organization of food protection behavior. These impairments were not attenuated by the administration of 3 mg/kg s.c. galanthamine twice daily. Results of this study suggest that the modest benefits afforded by galanthamine administration in DAT patients may not reflect improved attention or temporal orientation. Continued studies aimed at understanding the neural dysfunction underlying these deficits may lead to the development of novel therapeutic agents for DAT.

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Sonic hedgehog expression and glial reaction after neurotoxic lesion of adult mice spinal cord by Cholera Toxin-B Saporin

Gulino R, Gulisano M (2008) Sonic hedgehog expression and glial reaction after neurotoxic lesion of adult mice spinal cord by Cholera Toxin-B Saporin. Neuroscience 2008 Abstracts 124.14/B14. Society for Neuroscience, Washington, DC.

Summary: The spinal cord (SC) has ever been considered non-neurogenic because no neurons seem to be generated in the intact SC and only very few recent articles have reported spontaneous generation of new neurons after lesion. Conversely, many studies have demonstrated the occurrence of glial reaction after either mechanical or selective neurotoxic lesion. Sonic hedgehog (Shh) is a member of hedgehog family of secreted glycoproteins, which stimulate cell proliferation as well as neuron and oligodendrocyte differentiation during either development and adulthood. Few data are available about its role in the adult SC after injury. In this study, we used Cholera toxin-B saporin (CTB-sap), a retrogradely transported, ribosome-inactivating toxin, to induce a mild neurotoxic depletion of motoneurons within lumbar SC and to subsequently study the expression levels of Shh and the possible cell proliferation and differentiation within the depleted SC of young adult mice. After an injection of CTB-sap into the gastrocnemius muscle, we found a 30% depletion of lumbar SC motoneurons, and a comparable decrease of ChAT expression levels in the lumbar SC, one week after lesion. Moreover, we found a significant down-regulation of Shh expression, which significantly correlate with ChAT decrease. Both proteins recovered to near normal levels of expression at one month after lesion. The expression of ChAT also correlate with the performance of mice on a grid walk test. So, the observed spontaneous recovery of locomotion was associated with the spontaneous recovery of ChAT and Shh expression. Moreover, we observed a cell proliferation within the depleted SC parenchyma, which was associated with a visible increase of GFAP-positive astrocytes in the same area. Colocalization studies showed that the majority of these proliferating cells are active astrocytes. We hypothesized that Shh expression could have a role in both SC plasticity and the observed glial reaction after neurotoxic lesion. The restoration of normal levels of Shh during the first days after lesion could be a way to partially inhibit glial reaction and to improve functional recovery.

Related Products: CTB-SAP (Cat. #IT-14)

A brainstem generator for cutaneous allodynia associated with migraine headache

Edelmayer RM, Vanderah TW, Majuta L, Fioravanti B, De Felice M, Chichorro JG, Ossipov MH, King T,Lai J, Kori SH, Nelsen AC, Cannon KE, Heinricher MM, Porreca F (2008) A brainstem generator for cutaneous allodynia associated with migraine headache. Neuroscience 2008 Abstracts 171.15/LL16. Society for Neuroscience, Washington, DC.

Summary: Migraine patients often demonstrate cutaneous allodynia that begins unilaterally and intracranially and spreads, via unknown mechanisms, to contralateral and extracranial body regions. As cutaneous allodynia likely reflects the development of central sensitization, we hypothesized that descending facilitatory influences from the rostral ventromedial medulla (RVM) might underlie the generalized expression of this phenomenon. We employed a modified model of application of inflammatory mediators (IM) to the dura of unanesthetized animals and explored the possible requirement of a brainstem site for expression of generalized cutaneous allodynia. Rats were surgically implanted with two cannulas, one of which permitted the application of IM to the surface of the dura and the other for administration of compounds to the RVM, 7 days after surgery. Tactile withdrawal thresholds of the peri-ocular region of the face as well as the hindpaws were tested pre-surgery, post-surgery, and up to 6 hr after application of IM. Bupivacaine or YM022 (CCK2 receptor antagonist) were administered to the RVM at various times after IM. In some studies dermorphin-saporin was administered as a single microinjection to elicit a cytotoxic effect on presumed pain facilitation cells in the RVM; these rats were tested with IM after a further 28 days. Recordings of RVM “ON” and “OFF” cell activity were also performed in separate groups of naïve animals prior to, and after, IM application to the dura. Dural IM produced robust facial and hindpaw allodynia which peaked after approximately 3 hr and recovered to baseline thresholds by approximately 6 hr. RVM bupivacaine, YMO22, or cytotoxic destruction of pain facilitation cells had no effects on sensory thresholds alone, but prevented or significantly attenuated the expression of IM-induced cutaneous allodynia. In addition, IM applied to the dura produced a sustained increase in the discharge of RVM ON cells while transiently inhibiting OFF cells. Facial and hindpaw allodynia associated with dural stimulation may be a useful surrogate of migraine-associated pain which may be exploited mechanistically for the development of novel therapeutic strategies. The data demonstrate the requirement of descending facilitation from the RVM for the expression of cranial and extracranial cutaneous hypersensitivity and offer direct evidence of brainstem involvement in cutaneous allodynia associated with headache pain.

Related Products: CCK-SAP (Cat. #IT-31)

Lumbosacral-bulbo-spinal loop relayed by RVM on-cells regulates visceral nociception and modulates inhibitory effects of pregabalin and ondansetron

Sikandar S, Dickenson AH (2008) Lumbosacral-bulbo-spinal loop relayed by RVM on-cells regulates visceral nociception and modulates inhibitory effects of pregabalin and ondansetron. Neuroscience 2008 Abstracts 269.4/GG19. Society for Neuroscience, Washington, DC.

Summary: Descending controls from brainstem nuclei including the rostral ventromedial medulla (RVM) have been shown to play an important role in visceral pain, and compounds modulating serotonergic receptor activity and compounds targeting the α2δ subunit of voltage-gated calcium channels have demonstrated clinical efficacy in providing symptomatic relief in patients with visceral hyperalgesia. We investigated the role of RVM on-cells and a serotonergic lumbosacral-bulbo-spinal loop in visceral hyperalgesia and examined the antihyperalgesic effects of ondansetron and pregabalin in modifying visceral pain responses to colorectal distension (CRD) in rats. An in vivo model of visceral pain was established involving CRD and a reliable EMG recording protocol for measuring activity in the external oblique muscle following CRD for quantifying evoked visceromotor responses (VMR) in Sprague-Dawley rats. Changes in VMR evoked by CRD in a range of 10-80 mmHg were recorded following administration of ondansetron (50 μg/kg i.t.) and pregabalin (30 mg/kg s.c.) in naïve rats and rats pretreated with 0.25% intracolonic mustard oil (MO) to induce colonic hyperalgesia. Moreover, RVM on-cells were selectively ablated with injection of the neurotoxin saporin conjugated to the μ-receptor agonist dermorphin (DermSAP) using stereotaxic techniques. Twenty-eight days post-injection, the VMR were compared between naïve, SAP and Derm-SAP rats in control conditions and following intracolonic MO. CRD produced graded VMR responses that were facilitated by intracolonic MO. Both ondansetron and pregabalin were shown to effectively reduce evoked VMR to CRD in naïve rats and MO pretreated rats by antagonizing spinal 5-HT3 receptors and by binding to the α2δ subunit of voltage-gated calcium channels, respectively. Moreover, DermSAP pretreatment was shown to reduce overall evoked VMR, and the antihyperalgesic efficacies of ondansetron and pregabalin were also shown to be modified by the loss of on-cells in DermSAP rats. Furthermore, we verified immunohistochemically RVM on-cell ablation in DermSAP rats and quantified RVM 5-HT cell intensity between naïve, SAP and DermSAP rats. This study illustrates the role of 5-HT3-mediated descending facilitatory controls in visceral pain as well as providing evidence for the antihyperalgesic efficacy of the second generation α2δ ligand pregabalin in the CRD model. Moreover, evidence is provided for a facilitatory serotonergic lumbosacral-bulbo-spinal loop relayed by RVM on-cells that is evoked by CRD and modulates efficacies of pregabalin and ondansetron.

Related Products: Dermorphin-SAP / MOR-SAP (Cat. #IT-12)

Cholinergic depletion of the inferior temporal cortex interferes with recovery from episodic memory deficits

Croxson PL, Browning PGF, Gaffan D, Baxter MG (2008) Cholinergic depletion of the inferior temporal cortex interferes with recovery from episodic memory deficits. Neuroscience 2008 Abstracts 292.7/SS20. Society for Neuroscience, Washington, DC.

Summary: Cholinergic innervation of the temporal lobe has been suggested to have a role in episodic memory, a function which is also disrupted by lesions or disconnections of the medial temporal lobe circuit. Acetylcholine may be necessary for the specific function of some brain regions. Alternatively, it may be necessary for cortical plasticity and remodeling in those conditions in which the animal has to adapt following new task demands or injury. To investigate the role of cholinergic projections to inferotemporal cortex in episodic memory, and how loss of these projections might interact with damage to other brain structures necessary for normal memory function, we trained monkeys preoperatively on object-in-place scene discrimination problems until they could rapidly learn many problems within a testing session. Because learning occurs rapidly, mostly in a single trial, and depends on the presentation of discrimination problems in unique background scenes, this task models key features of human episodic memory. For the first stage of the experiment, the monkeys then received either a fornix transection or mammillary body ablation, both of which are known to impair learning in this task. All of the monkeys were impaired at scene learning after fornix or mammillary body lesions compared to their preoperative performance, consistent with previous results. In the second stage of the experiment, the monkeys underwent a second surgery in which we used the immunotoxin ME20.4-saporin to selectively deplete cholinergic inputs to the inferotemporal cortex. We then re-tested the monkeys on scene learning, and they were no more impaired than they were after their first surgery. This result is in striking contrast to an earlier finding by our laboratory that the effect of fornix transection is greatly exacerbated by prior depletion of acetylcholine from inferotemporal cortex (Browning et al. 2008, in press). The key difference between these two experiments is the order in which the lesions were placed: cholinergic depletion of inferotemporal cortex before fornix transection results in severe amnesia, whereas severe amnesia does not occur if the lesions are sustained in the opposite order. This finding suggests that monkeys require acetylcholine in inferotemporal cortex in order to adjust to the effects of a fornix lesion on episodic memory. This is consistent with a role for cholinergic input to neocortex in cortical plasticity and remodelling, rather than a specific role in certain brain functions such as episodic memory.

Related Products: ME20.4-SAP (Cat. #IT-15)

Cholinergic depletion of prefrontal cortex impairs acquisition of the delayed response task in rhesus monkeys

Baxter MG, Kyriazis DA, Croxson PL (2008) Cholinergic depletion of prefrontal cortex impairs acquisition of the delayed response task in rhesus monkeys. Neuroscience 2008 Abstracts 292.9/SS22. Society for Neuroscience, Washington, DC.

Summary: The involvement of corticopetal cholinergic projections in cognition remains difficult to define. Some investigators have suggested that normal cortical function requires an intact cholinergic input, whereas others emphasize a selective role of acetylcholine in attentional function or plasticity. Because of the anatomical and functional homology of human and macaque cortical structures, studies of the effects of selective ablation of cholinergic projections to cortical regions in the macaque would clarify the functions for which these projections are essential. We have tested 3 male rhesus monkeys with multiple bilateral injections of the immunotoxin ME20.4-saporin into lateral and orbital prefrontal cortex on a suite of cognitive tasks dependent on the integrity of orbital and ventrolateral prefrontal cortex, on which they were unimpaired. These tasks included new object-in-place scene learning, strategy implementation, and reinforcer devaluation. To determine the involvement of acetylcholine in dorsolateral prefrontal cortex function, we then trained these monkeys on the spatial delayed response task (Goldman, 1970; Bachevalier and Mishkin, 1986) in a manual testing apparatus. In this task the monkey watches as an experimenter places a small food reward in one of two wells of a test tray and then covers both wells with identical gray plaques. After a brief delay (1-5 sec) during which an opaque screen is interposed between the monkey and experimenter, the monkey is allowed to obtain the reward by displacing the plaque covering the well that was baited by the experimenter. Thus, the monkey must maintain the baited location (left or right) in memory during the brief delay interval in order to choose correctly. Performance of this task is devastated by ablation of dorsolateral prefrontal cortex. The monkeys with cholinergic depletion of lateral and orbital prefrontal cortex were also unable to learn the task to criterion, which four unoperated control monkeys learned readily. This finding suggests that acetylcholine, although not critical for functions of ventrolateral and orbital prefrontal cortex, is essential for dorsolateral prefrontal cortex function. An alternative explanation, which we are currently investigating, is that acetylcholine is necessary for the prefrontal cortex to adapt to the different task demands of delayed response, relative to the tests of discrimination learning with which these monkeys had extensive experience. This would be consistent with a role for cholinergic input to neocortex in cortical plasticity and remodeling.

Related Products: ME20.4-SAP (Cat. #IT-15)

The role of orexin in sexual behavior and sexual reward of the male rat

Di Sebastiano AR, Yong-yow S, Coolen LM (2008) The role of orexin in sexual behavior and sexual reward of the male rat. Neuroscience 2008 Abstracts 97.4/UU18. Society for Neuroscience, Washington, DC.

Summary: The hypothalamic neuropeptide orexin has been demonstrated to play a role in reward related to drugs of abuse and is potentially involved in regulation of natural rewarding behaviors. Male sexual behavior has been shown to activate orexin neurons and this behavior is altered by administration of orexin receptor agonists or antagonists. However, the exact role of orexin in male sexual performance, sexual motivation and reward is currently unclear. Therefore, the goal of the current study was to test the hypothesis that orexin plays a critical role in sexual behavior, motivation and reward. First, using Fos as a marker for neural activation, we investigated activation of orexin neurons following different parameters of sexual behavior in sexually naïve and experienced male rats. It was demonstrated that orexin neurons in the lateral hypothalamic area (LHA) and in the dorsal medial hypothalamus/perifornical (PFA-DMH) region become activated with presentation of the female and there is no further increase in activation with other components of mating (15-30% in LHA; 65-80% in PFA-DMH). Next, we tested the functional role of orexin utilizing orexin-cell body specific lesions. Adult male rats underwent lesion or sham surgery using the targeted toxin orexin-saporin or blank-saporin respectively. Following two weeks recovery, sexual behavior was recorded over the course of four mating trials. During the first mating trial, males with complete lesions showed significantly shorter latencies to mount and intromit. This suggests that lesions facilitated sexual performance in naïve animals. This facilitation was attenuated by sexual experience as lesions did not affect any parameter of sexual behavior in experienced animals. Next, runway tests were conducted to determine motivation to run towards a potential partner over two conditioning trials. Lesions did not alter sexual motivation, as lesion and sham males all demonstrated increased speed to run towards an estrous female during the second trial. Finally, a conditioned place preference (CPP) paradigm was conducted as a measure of sexual reward. All groups formed a conditioned preference for the mating-paired chamber, indicating that lesions did not significantly disrupt sexual reward. Overall, these findings suggest that orexin does not play a critical role in male sexual performance, motivation, and reward, however may be involved in general arousal related to sexual behavior.

Related Products: Orexin-B-SAP (Cat. #IT-20), Blank-SAP (Cat. #IT-21)

The ablation of hindbrain catecholamine neurons innervating medial hypothalamic nuclei abolishes glucoprivic feeding, but spares the orexigenic response to ghrelin

Emanuel AJ, Dinh TT, Ritter S (2008) The ablation of hindbrain catecholamine neurons innervating medial hypothalamic nuclei abolishes glucoprivic feeding, but spares the orexigenic response to ghrelin. Neuroscience 2008 Abstracts 85.2/RR15. Society for Neuroscience, Washington, DC.

Summary: Ghrelin is an orexigenic peptide synthesized in the stomach and secreted during fasting. Receptors for ghrelin are present in the brain and direct injection of ghrelin into the brain evokes feeding. Nevertheless, Y. Date et. al. (2002) have claimed that gastric vagal afferent neurons are the major pathway conveying ghrelin's signals for starvation and growth hormone secretion to the brain. Furthermore, this group (Date et. al., 2006), has reported that noradrenergic neurons transmit ghrelin’s orexigenic signals from the hindbrain to the hypothalamus. The latter assertion was based on the loss of ghrelin-induced feeding in rats injected into the arcuate nucleus (ARC) with anti-dopamine beta hydroxylase (DBH) conjugated to saporin (DSAP), which retrogradely destroys DBH-containing neurons. We previously showed that DSAP microinjection either into the hypothalamic paraventricular nucleus (PVH) or ARC abolished glucoprivic feeding. Since glucoregulatory responses include alterations of both feeding and growth hormone secretion, we reasoned that the same catecholamine neurons sensitive to glucoprivation may contribute to these responses following ghrelin. To investigate this issue further, we microinjected DSAP (n=7) or unconjugated saporin (SAP control, n=7) bilaterally into the PVH of Sprague-Dawley rats (approximately 400 g BW). Three weeks later, daytime tests for feeding responses to 2-deoxyglucose (2DG, 200 mg/kg, 4-hr test) and ghrelin (15 µg/kg, i.p., 2-hr test) were conducted. As expected, DSAP abolished 2DG-induced feeding. However, the response to ghrelin was not abolished in DSAP treated rats. In fact, feeding in response to ghrelin was significantly enhanced in DSAP-treated rats, compared to the control SAP group (p<0.05). These results confirm our prior findings relative to the role of catecholamine projections in glucoprivic responses, but they contradict the results previously reported by Date et. al. The difference between our injection sites (we injected DSAP into the PVH, and Date injected into the ARC) is not likely to account for the different results since injections of DSAP into either site eliminate DBH terminals throughout the medial hypothalamus and appear to lesion the same population of catecholamine neurons. Therefore, until more detailed analysis is conducted, we conclude that hindbrain catecholamine neurons are required for glucoprivic but not ghrelin-induced feeding.

Related Products: Anti-DBH-SAP (Cat. #IT-03)

Role of medial septum-diagonal band of Broca neurons in cognitive flexibility

Pang K, Janke K, Servatius RJ (2008) Role of medial septum-diagonal band of Broca neurons in cognitive flexibility. Neuroscience 2008 Abstracts 89.20/SS37. Society for Neuroscience, Washington, DC.

Summary: Cholinergic and GABAergic neurons are major components of the septohippocampal pathway, and comparisons between the two neuronal populations are important for understanding the function of medial septum and vertical limb of the diagonal band (MSDB). Recently, we have been investigating the importance of MSDB neurons in cognitive flexibility. Cognitive flexibility is commonly examined in procedures that require reversal of stimulus-reward associations and those that require shifts in attention set, involving switching attention to different stimulus dimensions. Our recent studies demonstrated that selective damage of GABAergic but not cholinergic MSDB neurons impaired spatial reversal. The present study will determine whether selective lesions of cholinergic or GABAergic MSDB neurons impairs shifting of attentional set. Sprague Dawley rats will be administered saline, GAT1-saporin or 192-IgG saporin into the MSDB to produce no damage, selective GABAergic damage or selective cholinergic damage, respectively. Verification of the lesions will be performed using immunocytochemistry at the end of the study. The behavioral procedure will occur in a plus maze. Rats will start in one of two arms opposite each other (i.e., north and south arms) randomized across trials. On any single trial, the arm opposite the starting arm will be blocked forming a T-maze. Rats will have a choice of entering one of the remaining 2 arms (east or west arms) for food reinforcement. Half of the rats will be reinforced to make an egocentric response (left or right turn) and the other rats will be reinforced to go to a particular arm (east or west; allocentric response) regardless of starting location. After reaching criterion (10 consecutive correct choices), the goal location will be reversed (i.e., left turn to right turn or east to west arm) or shifted to a different dimension (i.e., left turn to east arm or west arm to right turn). It is expected that rats treated with GAT1-saporin, but not 192-saporin, will be impaired on the reversal procedure, similar to previous studies. Impairments in shifting attention set would suggest a global impairment in cognitive flexibility. However, an impairment in the reversal procedure but not shifting of attention set would be similar to recently described deficits in the nucleus basalis magnocellularis using ibotenic acid and 192-IgG saporin lesions (Tait and Brown, Behav Brain Res. 187:100, 2008). The results of this study will provide important insight into the role of the MSDB in learning, attention and cognitive flexibility.

Related Products: 192-IgG-SAP (Cat. #IT-01), GAT1-SAP (Cat. #IT-32)

192-IgG Saporin lesions of the medial septum or nucleus basalis magnocellularis disrupt exploratory trip organization

Wallace DG, Winter SS, Martin MM, Mcmillin JL (2008) 192-IgG Saporin lesions of the medial septum or nucleus basalis magnocellularis disrupt exploratory trip organization. Neuroscience 2008 Abstracts 90.15/SS57. Society for Neuroscience, Washington, DC.

Summary: Previous work has demonstrated that rats use self-movement cues to organize their exploratory behavior. The hippocampus and several cortical areas have been implicated in processing self-movement cues. The current study investigated whether selective cholinergic deafferentation of the hippocampus or cortex differentially influenced the organization of exploratory behavior. Long Evans female rats received injections of 192 IgG-Saporin or saline into the medial septum (MS) or nucleus basalis magnocellularis (NB). Subsequent to recovery, rats were placed on a large circular table that provided access to a refuge under complete dark conditions (infrared cameras and goggles were used to visualize the rat). All rats established a home base in the refuge; however, impairments in exploratory trip organization specific to the homeward segment were observed in MS and NB rats. Both groups displayed increased variability in the temporal pacing of speeds on the homeward return, consistent with impaired distance estimation. Only the NB group displayed a significant reduction in stop duration after short, medium, and long searching progressions. These observations are consistent with different roles for hippocampal and cortical cholinergic function in processing self-movement cues.

Related Products: 192-IgG-SAP (Cat. #IT-01)

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