References

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.

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

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.

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

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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Martin MM, Winter SS, Cheatwood JL, Carter LA, Jones JL, Weathered SL, Wagner SJ, Wallace DG (2008) Organization of food protection behavior is differentially influenced by 192 IgG-saporin lesions of either the medial septum or the nucleus basalis magnocellularis. Brain Res 1241:122-135. doi: 10.1016/j.brainres.2008.09.018

Summary: In this work the authors used a food-protection model to investigate the role of cholinergic neurons in the processing of information from internal and external sources. Rats received the following amounts of 192-IgG-SAP (Cat. #IT-01): 15 ng or 20 ng into the medial septum (MS), or 20 ng into the nucleus basalis magnocellularis (NB). While the NB lesions reduced the number of successful food protection behaviors, lesions in the MS disrupted the temporal organization of this behavior.

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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.

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

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.

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

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)

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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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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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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