sfn2006

Northrop LE, Erskine MS (2006) Noradrenergic nuclei involved in sensory input during mating project to the ventromedial hypothalamus and are involved in mating-induced pseudopregnancy in female rats. Neuroscience 2006 Abstracts 661.23. Society for Neuroscience, Atlanta, GA.

Summary: The ventrolateral region of the ventromedial hypothalamus (VMHvl) is known to control female sexual receptivity through the activity of ovarian steroids in the female rat. These receptors are thought to aide in the steroid-dependent facilitation of the lordosis posture. Besides harboring estrogen and progesterone receptors, dense numbers of noradrenergic receptors are also present in the VMHvl. Previous research has shown that norepinephrine is released in significant amounts within the VMHvl after a female receives vaginocervical stimulation (VCS). At the time of mating, the vaginocervical sensory input travels from the brainstem, through the ventral noradrenergic bundle (VNAB), and finally to the VMH. Sufficient amounts of VCS are necessary for inducing twice daily prolactin surges, which are required for the initiation of pseudopregnancy (PSP). To distinguish whether these cells play a role in mating-induced PSP, they were selectively lesioned using the immunotoxin anti-dopamine-β-hydroxylase-saporin (DBH-SAP) 10 days prior to mating. Females were given bilateral VMHvl infusions of either 60ng/0.6µl of DBH-SAP or 2ng/0.6µl of IGG-SAP (non-specific control). Ten days following infusion on proestrous, females received one of two treatments: no VCS (home cage), or a sufficient amount of VCS (15 intromissions from males) to induce PSP. PSP was measured using vaginal smears and serum PRL concentrations. The next witnessed proestrous day after mating, females were mated again with the same type of stimulus as previously administered and perfused 90 min later. The brainstems were cut in 30µm sections, and ICC was used to visualize DBH and FOS immunoreactivity (IR). FOS-IR and DBH-IR cells were counted in the A2 and A1 cell regions, components of the VNAB. DBH-SAP infused females that received 15I showed 50% induction of PSP whereas IGG-SAP (15I) females showed 100% induction of PSP. None of the home cage rats became PSP . VMHvl DBH-SAP infusions significantly decreased DBH/FOS-IR expression in A2 and A1 nuclei, as well as decreased expression in DBH-IR in A2 nuclei compared to IGG-SAP infused females. Our results show that A1 and A2 noradrenergic cells which innervate the VMHvl are required for initiation of P/PSP.

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

Lu J, Yoshida K, Fuller PM, Saper CB (2006) Absence of a systemic febrile response to PGE2 and LPS following targeted saporin lesions of the rostral raphe pallidus. Neuroscience 2006 Abstracts 662.18. Society for Neuroscience, Atlanta, GA.

Summary: Anatomical studies have indicated that the rostral raphe pallidus (RPa) medullary area contains sympathetic premotor neurons that may be required for the fever responses triggered by prostaglandin E2 (PGE2) and lipopolysaccharide (LPS) administration. For example, stimulation of this region increases sympathetic activity to brown adipose tissue (BAT) and arteries of the tail, the two primary thermoregulator effector organ in the rat. In addition, neurons in this region are activated by cold exposure and central administration of PGE2. To better understand the role of the RPa in the systemic febrile response to endogenous and exogenous pyrogenic mediators, we performed targeted orexin-saporin lesions of the RPa. Following lesions of the RPa, the amplitude of core body temperature (Tb), as compared with pre-lesion measurements and controls, was significantly increased (p<0.001). Mean Tb did not differ between groups, however. In addition, fever responses to both i.p. LPS and i.c.v. PGE2 were completely blocked in the RPa lesioned rats. Importantly, following LPS administration, the RPa lesioned animals demonstrated the same pattern of Fos expression in the preoptic area as compared to intact controls, suggesting normal activation of the pyrogen-reception system. These observations establish a critical role for the RPa nucleus in the systemic fever response to the pyrogenic mediators LPS and PGE2.

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Torner EK, Flesher MM, Chavez CM, Linton KD, Herbert MS, Butt AE (2006) 192 IgG-saporin lesions of the cholinergic basal forebrain disrupt attention and awareness in Pavlovian trace but not delay conditioning in rats. Neuroscience 2006 Abstracts 667.19. Society for Neuroscience, Atlanta, GA.

Summary: Recent research suggests that Pavlovian trace conditioning, but not delay conditioning, requires awareness or attention, where these processes appear to depend on specific brain systems. For example, past research has shown that although amnesiac humans with damage to the hippocampus (HPC) acquire a normal conditioned response (CR) in delay conditioning paradigms where the conditioned stimulus (CS) and unconditioned stimulus (US) partly overlap, they fail to acquire the CR in trace conditioning paradigms where the CS and US are separated in time. Others have shown that the anterior cingulate cortex (ACC) is similarly necessary for trace but not delay conditioning in rats. Another study in rabbits also suggests medial prefrontal cortex (mPFC) involvement in trace but not delay conditioning. The basal forebrain cholinergic system (BFCS) has projections to mPFC, ACC, and HPC. Given that each of these regions is critical for trace but not delay conditioning, we hypothesized that lesions of the BFCS using 192 IgG-saporin (SAP) would selectively impair trace but not delay appetitive conditioning in rats. Rats received bilateral injections of SAP or saline only (sham lesion control group) into BFCS prior to conditioning with a white noise CS and sucrose pellet US in either a delay or 10 s trace conditioning paradigm. Results supported our hypotheses, with the BFCS lesion group showing normal delay conditioning but impaired trace conditioning. In order to assess the potential for distraction to exacerbate the observed BFCS lesion-induced impairments in trace conditioning, a visual distracter (continuously flashing light) was added to the trace conditioning paradigm in a second experiment. Given evidence suggesting BFCS involvement in attention, it was hypothesized that the addition of a visual distracter to the trace conditioning task would cause a greater degree of impairment in the BFCS lesion group than in the control group tested in that task. Preliminary data support this hypothesis. Together, these experiments suggest that the BFCS is necessary for normal trace conditioning, which is argued to require both awareness and working memory. The additional impairment in trace conditioning caused by the visual distracter further suggests a role for the BFCS in mediating attention.

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Van Kampen JM, Eckman CB (2006) Cholinergic agonists restore deficits in hippocampal neurogenesis after basal forebrain lesions in the adult rat brain. Neuroscience 2006 Abstracts 674.13. Society for Neuroscience, Atlanta, GA.

Summary: Discrete regions of the adult CNS, including the dentate gyrus of the hippocampus, retain the capacity for neurogenesis. Progenitor cells in these regions may represent a potential source of endogenous cells for replacement therapies in neurodegenerative diseases. In order to facilitate the development of such therapeutic approaches, an understanding of the microenvironmental signals regulating neurogenesis in the adult brain is essential. Small molecule neurotransmitters, such as acetylcholine, have been shown to regulate neurogenesis both during development and in the adult brain. In the studies presented here, we examine the effects of various cholinergic agonists on hippocampal neurogenesis in the adult rat brain. Intraventricular administration of a nicotinic agonist significantly attenuated proliferation, while muscarinic agonists triggered a dose-dependent increase in neurogenesis within the dentate gyrus and CA1 regions of the hippocampus. This effect was blocked by the M1 receptor-selective antagonist, pirenzepine. The basal forebrain provides an abundant source of cholinergic input to the hippocampus, thought to play an important role in learning and memory and Alzheimer’s disease (AD) pathophysiology. Loss of this cholinergic innervation, as occurs in AD, was achieved by a selective immunotoxin and resulted in a significant reduction in hippocampal neurogenesis. This loss of neurogenesis was reversed by intraventricular administration of a muscarinic receptor agonist. The loss of basal forebrain cholinergic inputs observed in AD may contribute to deficits in learning and memory through reductions in hippocampal neurogenesis. The results reported here suggest that pharmacological manipulation of the cholinergic system may represent a means of stimulating hippocampal neurogenesis as a potential treatment strategy.

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

Sengelaub DR, Osborne MC, Little CM, Huyck KD, Verhovshek T (2006) Neuroprotective effects of testosterone in two models of spinal motoneuron injury. Neuroscience 2006 Abstracts 683.12. Society for Neuroscience, Atlanta, GA.

Summary: Following induced death or axotomy of spinal motoneurons remaining motoneurons atrophy, but this atrophy can be reversed or prevented by treatment with testosterone (T). For example, partial depletion of motoneurons from the highly androgen-sensitive spinal nucleus of the bulbocavernosus (SNB) induces dendritic atrophy in remaining motoneurons, and this atrophy is prevented by treatment with T. To test whether T has similar effects in more typical motoneurons, we examined potential neuroprotective effects in motoneurons innervating muscles of the quadriceps. Motoneurons innervating the vastus medialis muscle were selectively killed by intramuscular injection of cholera toxin conjugated saporin. Simultaneously, some saporin-injected rats were given implants containing T or left untreated. Four weeks later, motoneurons innervating the ipsilateral vastus lateralis muscle were labeled with cholera toxin conjugated HRP, and dendritic arbors were reconstructed in 3 dimensions. Compared to intact control males, partial motoneuron depletion resulted in decreased dendritic length (70%) and soma size (13%) in remaining quadriceps motoneurons, but as in the SNB, this atrophy was attenuated by T treatment. In a second model, brain-derived neurotrophic factor (BDNF) and T have a combinatorial effect in the maintenance of motoneurons after axotomy in that dendritic morphology is supported by BDNF treatment, but only in the presence of T. Using immunohistochemical methods, we examined the regulation of the expression of the BDNF receptor, trkB, by T. In both the highly androgen-sensitive motoneurons of the SNB and the more typical quadriceps motoneurons, the expression of trkB receptors was regulated by the presence of T. Motoneurons of castrated animals deprived of T show reduced expression of trkB receptors compared to motoneurons of intact animals or castrated animals given T replacement. This finding suggests that maintenance of trkB receptors with T may be necessary to permit the trophic effects of BDNF in supporting dendritic morphology after axotomy. Together, these findings suggest that T regulates neuroprotective effects through a variety of mechanisms, not only in highly androgen-sensitive motoneurons, but in more typical motoneuron populations as well.

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

Iacobucci P, Colonnello V, Ricceri L (2006) Detailed analysis of ultrasound vocalizations emitted by 12-d-old rats during homing test: effects of a brief reunion with littermates in neonatal basal forebrain cholinergic lesioned pups. Neuroscience 2006 Abstracts 374.17. Society for Neuroscience, Atlanta, GA.

Summary: To evaluate the role of the developing cholinergic basal forebrain system on neonatal behavioural repertoire, seven day-old rats received lesions using intraventricular injections of 192 IgG-saporin or saline; on postnatal day (pnd) 12 we recorded ultrasonic vocalizations (USVs) emitted during a homing test (an olfactory based test carried out in a T-shaped arena to measure discrimination of home- versus non familiar- nest odors). USVs emitted by isolated 12-day-old pups were recorded during a first exposure to the homing test (4 min) and during a second exposure in the same setting (4 min), after a 1 min reunion with littermates. In all pups (control and 192 IgG-saporin) number of USVs (ranging between 30 and 60 kHz) significantly increased after reunion with littermates. Analysis of the sonographic structure of the pup calls identified 15 different classes of signals and revealed that the increase in USVs after reunion with littermates was due to a selective increase in 4-5 of the 15 classes [namely, constant frequency signals, brief calls (dot-shape), multiple sweeps calls (e.g. M- or W-shape), rising sweeps (/)]. Also time spent over the home-scented area increased during the second exposure to the homing test in all pups, but such increase was more evident in control than in cholinergic lesioned pups. Even if effects of the neonatal cholinergic lesions were limited, from a methodological point of view these results suggest that USV emission can be measured not only in standard neonatal isolation settings, but also while the subject is performing another neonatal behavioral task. Interestingly, the USV emission during the homing test is modulated by the rat pup after a brief reunion with littermates (a phenomenon resembling the “maternal potentiation”). Such modulation affects both quantitative and qualitative USV features, as well as the time spent by the pups over the home-scented area.

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

McKay LC, Feldman JL (2006) Unilateral ablation of neurokinin-1 receptor-expressing (NK1R) neurons within the preBötzinger complex (preBötC) in adult rats disrupts breathing during sleep but not during wakefulness. Neuroscience 2006 Abstracts 455.4. Society for Neuroscience, Atlanta, GA.

Summary: In adult rats, as the number of ablated preBötC NK1R neurons increases, breathing becomes increasingly disrupted during sleep(1), eventually resulting in an ataxic breathing pattern during wakefulness when cell loss is >80%(1,2). Here we determine whether ablation of fewer preBötC NKIR neurons leads to sleep-disordered breathing (SDB), while breathing during wakefulness remains stable. Adult male Sprague Dawley rats (n=8) were anesthetized (100mg/kg Ketamine, 10mg/kg Xylazine i.p.) and instrumented to record diaphragmatic, abdominal and neck EMG, ECG, and EEG. Fourteen days post-implantation a second surgery was performed to stereotaxically inject unilaterally into the preBötC, the toxin saporin conjugated to substance P (SP-SAP), which selectively ablates NK1R neurons. Rats were kept on a 12-hour light/dark cycle and monitored within a plethysmograph from day 1 post-injection until they were sacrificed (days 21-50). Post-unilateral SP-SAP injection, respiratory pattern remained normal during wakefulness and sleep until ~day 9. At this point, respiratory pattern during sleep, particularly REM sleep, became increasingly disordered. The disruptions in breathing pattern were characterised by an increase in frequency of apneas and hypopnea (~4-6/hour of sleep vs <3 pre-injection control; p<0.05). Rats that were monitored up to 50 days post-SP-SAP injection continued to have SDB, while breathing during resting wakefulness remained stable. Unlike bilateral SP-SAP injected rats, an ataxic breathing pattern did not develop during wakefulness(1,2). Histological analysis of the ventrolateral medulla confirmed that only NKIR neurons within the preBötC on one side of the medulla were ablated (~300 preBötC NK1R neurons/side in the adult rat). Unilateral SP-SAP injection results in SDB, while breathing during resting wakefulness appears normal. Over time, breathing during sleep does not improve. We have previously proposed that in the elderly and in individuals who suffer from various neurodegenerative diseases, gradual loss of preBötC NK1R neurons may explain why SDB is highly prevalent in these populations. We further speculate that SDB can go unnoticed because breathing during wakefulness is relatively stable.

Related Products: SP-SAP (Cat. #IT-07)

Ho N, Han S, Dawe GS (2006) Effect of running on neurogenesis in cholinergic lesioned mice. Neuroscience 2006 Abstracts 318.5. Society for Neuroscience, Atlanta, GA.

Summary: Neurogenesis occurs mainly in two regions of the adult rodent brain, the dentate gyrus of the hippocampus and the subventricular zone. There are many factors which regulate neurogenesis, but voluntary exercise has consistently been shown to enhance neurogenesis. Exercise has been reported to specifically stimulate neural cell proliferation in the hippocampus but not the olfactory bulb. One of the major sources of afferents to the hippocampus are the septohippocampal projections, in which axons from the medial septum and diagonal band of Broca (MSDB) project to the hippocampus. Major components of the septohippocampal pathway that act as ‘pacemakers’ for hippocampal theta rhythm, which increases in conjunction with the voluntary running, are the cholinergic and GABAergic projections rising from cells in the MSDB. This present study investigates the effect of a partial cholinergic lesion in the basal forebrain and MSDB of mice, a partial model of the neurodegeneration that occurs in Alzheimer’s disease, on neural cell proliferation and neurogenesis. Murine p75-SAP, a conjugate of a p75 antibody that targets selectively cholinergic cells and cytotoxic saporin, was injected into the ventricles of female adult Swiss mice. After recovery from surgery mice were then administered bromodeoxyuridine (BrdU). BrdU immunopositive cells were quantified 24 hours and 4 weeks to assess for neural cell proliferation and survival of newly generated cells. Partial cholinergic denervation led to a decrease in the survival of new born cells in the dentate gyrus. We compared the effects of voluntary running for a period of 12 days in non-lesioned and lesioned mice under similar experimental conditions. Running resulted in an increase in neural cell proliferation for both the non-lesioned and lesioned groups. Running led to a marked increase in cell proliferation in lesioned mice compared to the controls, and also enhanced neurogenesis, as determined by the colocalization of BrdU and the neuronal nuclei marker NeuN in cells within the dentate gyrus. The present study suggests that voluntary running may have a positive effect on neurogenesis in neurodegenerative models in rodents. Further work needs to be done to elucidate the underlying mechanisms of exercise-induced neurogenesis.

Related Products: mu p75-SAP (Cat. #IT-16)

Li A, Nattie EE (2006) Lesions of neurokinin-1 receptor immunoreactive (NK1R-ir) neurons in the ventral medulla decrease chemoreception and ventilation. Neuroscience 2006 Abstracts 455.5. Society for Neuroscience, Atlanta, GA.

Summary: We injected SSP-saporin, a toxin specific for NK1R-ir neurons, into the cisterna magna in order to lesion a wide aspect of the ventral medulla. NK1R-ir loss after 21 days was 79% in the retrotrapezoid nucleus, 65% in the A5 region, 38% in the medullary raphe and 49% in the pre-Botzinger complex. This resulted in a large reduction in the ventilatory response to 7% CO2 during wakefulness (-61%) and NREM sleep (-57%). The response to 12% O2 was reduced by 35-40% at 8 days but partially recovered by 22 days. We did not measure chemoreception in REM sleep. Ventilation in wakefulness, NREM and REM sleep measured over 4 hrs of air breathing decreased by 12-13% at 21 days compared to baseline values (P< 0.005, one-way repeated measures ANOVA; P< 0.05 post hoc comparison, Dunnett’s test). In REM sleep compared to awake and NREM sleep, the rats breathed with a higher frequency and smaller tidal volume, a pattern that was unaffected by the lesion, and with a greater coefficient of variability, which was further increased by the lesion (71 +/- 4 % vs 34 +/- 6 %). We did not observe any severe rhythm disturbances. We attribute the effect of these lesions, which are greatest in the ventral medullary regions including the retrotrapezoid nucleus and the medullary raphe, to loss of tonic chemoreceptor input. This input seems to have equal weight in wakefulness and in NREM and REM sleep and it seems to minimize the variability of frequency observed in REM sleep.

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Rapp KL, Khan AM, Watts AG (2006) Catecholaminergic afferents are required for hypothalamic parvicellular paraventricular neurons to transduce signals associated with hypoglycemia into p44/42 MAP kinase phosphorylation events. Neuroscience 2006 Abstracts 355.9. Society for Neuroscience, Atlanta, GA.

Summary: Hypoglycemia activates CRH neuroendocrine neurons in the hypothalamic paraventricular nucleus (PVH), thereby rapidly elevating plasma ACTH and corticosterone concentrations. Hindbrain-originating catecholaminergic (CA) neurons projecting to the PVH facilitate ACTH release after insulin-induced hypoglycemia; however, the intracellular signaling mechanisms that CRH neurons use to transduce CA signals into secretogogue function are unknown. We have previously shown that p44 and/or p42 MAP kinases (ERK1/2) are phosphorylated in CRH neurons after 2-deoxy-D-glucose challenge (Endoc. v145:351, 2004). We now ask: Are hindbrain-originating CA projections to the PVH essential for ERK1/2 phosphorylation in response to insulin-induced hypoglycemia? Male Sprague-Dawley rats received acute bilateral PVH microinjections of either saporin toxin conjugated (DSAP) to an antiserum against dopamine beta hydroxylase (DBH) or conjugated to a non-targeted mouse IgG (control mIgG-SAP), were fitted with jugular catheters, and allowed to recover. On the day of testing, plasma glucose was measured just before the onset of hypoglycemia (induced via insulin bolus [2U/kg, i.v.]) and then 10 and 30 min thereafter. Rats were then anesthetized and transcardially perfused. Brain tissue processed for dual immunofluorescence using antibodies raised against DBH and phospho-ERK1/2 was visualized by confocal microscopy. Baseline plasma glucose levels did not differ significantly between groups (5.66 ± 0.26 mM), but were significantly reduced in each group when compared to baseline after 10 (1.48 ± 0.12 mM) and 30 (1.92 ± 0.12 mM) minutes. DSAP rats displayed marked loss of DBH immunostaining in the PVH relative to controls, with concomitant loss of phospho-ERK1/2 immunostaining within the parvicellular PVH. Further analysis was performed to address the effect of DSAP on DBH staining and ERK1/2 recruitment in the hindbrain and arcuate nucleus. Our results confirm that phosphorylation of ERK1/2 in parvicellular PVH after insulin-induced hypoglycemia requires intact CA afferent innervation. These data contribute to our understanding of how intracellular signaling is regulated in parvicellular PVH neurons. They also underscore an emerging importance of CA afferents for mediating neuroendocrine responses to systemic alterations in glucose.

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