sfn2007

I’Anson H, Jethwa PH, Tanna GA, Pattinson LM, Ebling FJP (2007) Histaminergic regulation of energy homeostasis in the Siberian hamster. Neuroscience 2007 Abstracts 629.17/YY20. Society for Neuroscience, San Diego, CA.

Summary: We tested the hypothesis that posterior hypothalamic histaminergic (HA) activity regulates energy homeostasis in the Siberian hamster during long day (breeding season) photoperiods. Adult male Siberian hamsters were given bilateral injections of the retrogradely transported ribosomal toxin, saporin, conjugated to orexin-B receptor antibody (OXSAP, 200 nl, 92 ng/ul) into the posterior hypothalamus (PH) to selectively destroy HA neurons, the majority of which possess orexin-B receptors. Controls were injected with unconjugated saporin (sham). Metabolic rate (VO2 ml/kg0.75/h), ingestive behavior and locomotor activity were monitored using the comprehensive lab animal monitoring system (CLAMS, Columbus instruments). Body weight was significantly decreased by day 12 post-surgery in OXSAP compared with sham hamsters and remained significantly lower throughout the 5 month study, even though food intake was comparable between groups. At 3 months post-surgery, OXSAP food intake was significantly higher in the dark (p< 0.05) and significantly lower in the light phase (p<0.05), but not different overall between groups. In addition, the frequency of feeding bout tended to be lower during dark and light phases compared with sham hamsters (p=0.07). Lower body weight with no overall change in food intake suggests an increase in energy expenditure in the OXSAP hamsters. Consistent with this interpretation, locomotor activity in OXSAP hamsters tended to be higher during the dark phase (p=0.09), but not in the light phase. In addition, metabolic rate was significantly higher during the first two hours of the dark phase compared with sham hamsters (p<0.05), and tended to be higher during the entire dark phase (p=0.08). During a second CLAMS study (4 months post-surgery), metabolic rate was monitored following injection of an H3 receptor antagonist (thioperamide, 30 mg/kg, ip) as a probe to determine if any significant HA cell loss had occurred. Metabolic rate was significantly lower during the first 2 hours after thioperamide in sham hamsters, but not in OXSAP hamsters, suggesting that HA regulation of energy balance had been compromised by the OXSAP lesion. Immunohistochemical results confirmed 63-96% loss of HDC-immunoreactivity in magnocellular neurons of the posterior hypothalamus in the OXSAP group. These data support the hypothesis that posterior hypothalamic HA neuron activity modulates metabolic activity during the breeding season in the Siberian hamster, although it is likely that ablation of additional neuronal phenotypes which express orexin-B (e.g. MCH) may contribute to the observed metabolic effects.

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

Winter SS, Martin MM, Wallace DG (2007) Walking the Plank: Role of the medial septum in distance estimation. Neuroscience 2007 Abstracts 743.21/BBB15. Society for Neuroscience, San Diego, CA.

Summary: Controversy surrounds the role of the septohippocampal system in spatial orientation. Recent work has demonstrated that selective cholinergic deafferentation of the hippocampus impairs use of self-movement cues while sparing environmental cue use. Self-movement cues are generated from changes in position or direction. The current study examines the role of the septohippocampal cholinergic system in processing of self-movement cues related to changes in position or distance estimation in a food hoarding task. The probability of food hoarding has been shown to be influenced by travel distance and time to consume the food item. Long Evans female rats received either injections of 192 IgG-Saporin (SAP) or saline (SHAM) into the medial septum. Subsequent to recovery, rats were placed in a refuge on a 15 cm wide plank and allowed to traverse the plank to collect food pellets located at the end. Both the distance to the food pellet (2.4 vs. 4.8 m) and size of the food pellet (190, 500, 1000 mg) were varied across days. Differences in food hoarding probability were observed between groups. SAP rats were less likely to modify their food hoarding probability in response to changes in plank length relative to SHAM rats. These results are consistent with selective hippocampal cholinergic deafferentation producing deficits in processing self-movement cues related to distance estimation.

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

King M, Jentsch JD (2007) Prefrontal cortical norepinephrine depletion does not impair spatial working memory in rats. Neuroscience 2007 Abstracts 645.16/CCC18. Society for Neuroscience, San Diego, CA.

Summary: The midbrain dopamine neurons are thought to encode a reward prediction error signal (Schultz et al., 1997; Bayer & Glimcher, 2005). Parkinson’s disease (PD) is characterized by a loss of nigral dopamine neurons. Dopaminergic drugs including the dopamine precursor L-Dopa and D2 receptor agonists are taken to relieve disease symptoms. We hypothesized that patients with moderate PD (1) show atypical reinforcement learning off dopaminergic medication due to dopamine neuron loss, and (2) show more normal reinforcement learning on dopaminergic drug therapy. We developed a method to rapidly assess reinforcement learning in human subjects (Rutledge et al., SfN 2005) adapted from matching law tasks used in monkeys (Sugrue et al., 2004; Lau & Glimcher, 2005). On each trial, subjects choose one of two animated crab traps. Rewards (crabs worth $0.10) were scheduled for the two targets with different independent rates. Scheduled rewards remained available until the associated target was chosen, as in the original matching law experiments (Herrnstein, 1961). After a 5-minute training period, subjects completed 800 trials as we varied reward probabilities across blocks. PD patients (n=19) completed one session on and one off dopaminergic medication. Age-matched controls (n=21) and healthy young subjects (n=20) completed one session. We found that young and elderly control subjects had similar reinforcement learning rates, but learning rates were reduced in PD patients (when tested off medication). Learning rates in the same PD patients were restored to control levels when dopaminergic drugs were administered. We also found that the reinforcement-independent strategies of our subjects were influenced by dopamine. Young subjects tended to alternate targets independent of reward history. In contrast, elderly subjects (who suffer some dopamine neuron loss) had a tendency to perseverate in their choices. This tendency was increased in PD patients (off medication), but restored to control levels when dopaminergic drugs were administered. This effect on choice is not explained by existing models of dopamine function. These data support a role for dopamine in human reinforcement learning. Future models of decision making in reinforcement learning tasks must also account for a reward-independent effect of dopamine on choice behavior.

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

Tai S, Ma J, Leung L (2007) Vestibular activation stimulates cholinergic system in the hippocampus. Neuroscience 2007 Abstracts 399.21/OO13. Society for Neuroscience, San Diego, CA.

Summary: The vestibular system has been suggested to participate in spatial navigation, a function ascribed to the hippocampus. We examined the mechanisms that induced hippocampal theta, a 4-10 Hz rhythm in the electroencephalogram (EEG), during vestibular activation in rats. Freely behaving rats were rotated at various speeds, on a vertical axis, in the light or dark. Hippocampal EEGs were recorded by implanted electrodes in hippocampal CA1, and analyzed by spectral analysis. A clear hippocampal theta rhythm was induced during immobility by rotations at different speeds (20-70 rpm). The rotation-induced theta was abolished, in light and dark settings, by muscarinic cholinergic receptor antagonist atropine sulfate (50 mg/kg i.p.) but not by atropine methyl nitrate (50 mg/kg i.p.), which did not pass the blood-brain barrier. Rotation-induced theta was attenuated in rats in which the cholinergic neurons in the medial septum (MS) were lesioned by 192 IgG-saporin (0.14 µg/0.4 µl infused bilaterally into the MS 10-20 days prior to the experiments). Cholinergic lesion in the MS was confirmed by a depletion of MS neurons that stained positively for choline acetyltransferase and an absence of acetylcholinesterase histochemical staining in the hippocampus. Bilateral lesion of the vestibular receptors (by 0.1 ml intratympanic injection of 300 mg/ml sodium arsanilate) also attenuated the rotation-induced theta rhythm. Vestibular lesion was confirmed by the contact righting test where lesioned rats will “walk” upside down on a Plexiglas sheet placed in contact with the soles of the feet while intact rats will right themselves immediately. In summary, an atropine-sensitive hippocampal theta is activated by septohippocampal cholinergic neurons which are in turn activated by vestibular stimulation. Vestibular-activated septohippocampal cholinergic activity is likely an important component of spatial navigation.

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

Burk JA, Altemose KE, Lowder MW (2007) Effects of spatial cueing on visual discrimination performance of rats following loss of basal forebrain corticopetal cholinergic neurons. Neuroscience 2007 Abstracts 424.4/HHH3. Society for Neuroscience, San Diego, CA.

Summary: Basal forebrain corticopetal cholinergic neurons are necessary for normal attentional performance. However, the exact attentional task parameters that are sufficient for inducing deficits following loss of basal forebrain corticopetal cholinergic neurons remain unclear. In Experiment 1, rats were trained to perform a spatially cued visual discrimination task (press a lever under an illuminated panel light) with explicit attentional demands removed. Animals then received infusions of the cholinergic immunotoxin, 192IgG-saporin, or saline into the basal forebrain. All animals were then tested in the same task trained before surgery and then task parameters, including the duration of visual signals and the inter-trial interval, were manipulated in order to tax attentional processing. Lesioned animals exhibited an initial increase in response latencies immediately following surgery but this deficit was not observed when task demands were increased. When the task was modified to remove spatial cueing, by presenting visual signals or no signal from a centrally-located panel light, lesioned animals exhibited an increase in lever press latencies compared to sham-lesioned animals. In Experiment 2, rats were trained in a visual discrimination task that, within each session, had blocks of trials with or without spatial cueing, using procedures similar to Experiment 1. After receiving intra-basalis infusions of 192IgG-saporin or saline, animals were tested for 12 sessions in the same task trained before surgery followed by one session in which the inter-trial interval was decreased. Lesioned animals did not exhibit deficits immediately following surgery, but did show elevated lever press latencies compared to sham-lesioned animals when the inter-trial interval was decreased. There was a trend for this lesioned-induced deficit to be more pronounced when spatial cues were not present. These experiments indicate that cortical acetylcholine is critical for maintaining normal visual discrimination performance when spatial cueing is not available. We speculate that, under conditions in which spatial cueing is unavailable, the lesion-induced increased lever press latencies reflect a disruption in recalling rules for an appropriate response.

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

Butt AE, Amodeo D, Flesher M, Marsa K, Holt R, Lladones R, Olney R, Haynes J, Kinney-Hurd BL, Dach N (2007) 192 IgG-saporin lesions of the cholinergic basal forebrain disrupt selective attention and trace conditioning but spare delay and long-delay conditioning. Neuroscience 2007 Abstracts 424.9/HHH8. Society for Neuroscience, San Diego, CA.

Summary: Recent research suggests that Pavlovian trace conditioning, but not delay conditioning, is a form of declarative memory that requires attention, where both of these processes 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) in rats and the medial prefrontal cortex (mPFC) in rabbits are similarly necessary for trace but not delay conditioning. The basal forebrain cholinergic system (BFCS) has projections to the 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 or long-delay appetitive conditioning in rats. Additionally, given evidence suggesting BFCS involvement in attention, it was hypothesized that the addition of varying levels of distraction during the trace conditioning task would cause progressively greater degrees of impairment in the BFCS lesion groups compared to controls. In contrast, neither the control groups nor the BFCS lesion groups were expected be negatively affected by the addition of a distracting stimulus in the delay and long-delay conditioning tasks. Rats received bilateral SAP lesions or sham lesions of the BFCS prior to conditioning with a white noise CS and sucrose pellet US in either a delay, long-delay, or 10 s trace conditioning paradigm. Separate groups of BFCS lesion and control rats were subjected to varying levels of visual distraction (flashing house light) in each paradigm; no distraction, low distraction (continuously blinking light), and high distraction (intermittent, unpredictable flashing light). Results supported our hypotheses, with the BFCS lesion groups showing normal delay and long-delay conditioning regardless of level of distraction. In contrast, trace conditioning was impaired in the BFCS lesion groups, with progressively greater degrees of impairment occurring with greater levels of distraction, and complete disruption of learning in the high distraction condition. Together, these experiments suggest that the BFCS is necessary for normal trace conditioning, and that the BFCS is critically involved in selective attention tasks where animals must discriminate relevant stimuli from distracting background stimuli.

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

Likhtik E, Popa D, Apergis-Schoute J, Fidacaro GA, Pare D (2007) Lesion of intercalated (ITC) amygdala neurons interfere with extinction of classically conditioned fear responses. Neuroscience 2007 Abstracts 426.6/HHH29. Society for Neuroscience, San Diego, CA.

Summary: The acquisition of conditioned fear responses (CRs) is thought to involve the potentiation of synapses conveying information about the conditioned stimulus (CS) to the basolateral (BLA) amygdala. Expression of CRs would depend on the transfer of potentiated CS inputs by the BLA to the central amygdala (CE). In contrast, the mechanisms of extinction remain controversial. It has been proposed that ITC neurons, which receive BLA inputs and generate feedforward inhibition in CE, are in a key position to mediate extinction. In this view, NMDA-dependent potentiation of BLA inputs to ITC cells during extinction training, would dampen the impact of CS-related BLA activity on CE neurons, inhibiting CRs. However, this idea is difficult to test because ITC cells occur in small, lateromedially dispersed clusters, making conventional lesioning methods inadequate. Here, we took advantage of the fact that, compared to the rest of the amygdala, ITC cells express a much higher concentration of mu opioid receptors (muORs). As a result, we could lesion them by performing local injections of a peptide-toxin conjugate (demorphin conjugated to saporin, D-Sap) that selectively targets cells expressing muORs. Control rats received injections of saporin conjugated to a blank peptide (B-Sap). On Day 1, intact rats were subjected to a standard cued fear conditioning protocol in context A. On Day 2, they received 20 CS alone presentations in a different context (B). On Day 3, rats then received either D-Sap or B-Sap injections in the ITC cell masses. One week later, extinction recall was tested in context B with 10 CS alone presentations. Compared to control (B-Sap) rats (n=10), ITC-lesioned rats (n=5) had an extinction deficit (ANOVA, F=11.687, p = 0.005). Post-hoc t-tests comparing % time freezing during the first five or last five CSs revealed that rats with ITC lesions had significantly higher freezing levels throughout the extinction recall test (p<0.002 for both tests). These differences were not attributable to a non-specific increase in freezing or anxiety levels as exploratory behaviors in a novel open field in control and ITC-lesioned rats were indistinguishable. Overall, these results indicate that ITC cells are involved in the expression of extinction.

Related Products: Dermorphin-SAP / MOR-SAP (Cat. #IT-12), Blank-SAP (Cat. #IT-21)

Arias-Carrion O, Hernandez-Martinez H, Drucker-Colin R (2007) Hypocretin/orexin neuronal loss increases adult neurogenesis. Neuroscience 2007 Abstracts 456.14/C7. Society for Neuroscience, San Diego, CA.

Summary: Adult neurogenesis in the subventricular zone (SVZ) is subjected to physiological regulation and can be modified by brain injuries. The sleep disorder narcolepsy may now be considered a neurodegenerative disease, as there is a massive reduction in the number of neurons containing the neuropeptide, hypocretin (HCRT). In the present study, we investigate the relationship between hypocretin neuronal loss and adult neurogenesis. The neurotoxin, hypocretin-2-saporin (HCRT2-SAP), was administered bilaterally to the lateral hypothalamus (LH) to lesion HCRT neurons. Five weeks after HCRT2-SAP administration a loss of HCRT-ir neurons into LH was produced. In normal animals, a high density of HCRT-ir fibers was found in the septum and was poor in the corpus callosum and striatum. These densities decreased in lesioned animals. To label dividing cells, we used 5-bromo-2′-deoxyuridine (BrdU). BrdU was injected twice daily during days 10-14 after lesion, saline or control procedure. Animals were killed at 3 weeks after the last BrdU injection. Experimental depletion of HCRT in rats increases precursor cell proliferation in the SVZ and subependimal layer of 3rd ventricle. However, we don’t find BrdU/HCRT double-labeled cells in the subependimal zone or LH. These observations suggest that the HCRT is a negative factor in adult neurogenesis.

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

Ma J, Tai S, Leung LWS (2007) Ketamine-induced gating deficit of hippocampal auditory evoked potentials in rats is alleviated by medial septum inactivation and antipsychotic drugs. Neuroscience 2007 Abstracts 498.12/GG19. Society for Neuroscience, San Diego, CA.

Summary: Gating of sensory responses is impaired in schizophrenic patients and animal models of schizophrenia. Ketamine, an N-methyl-D-aspartate receptor antagonist, is known to induce schizophrenic-like symptoms in humans. In this study, we investigated some conditions underlying ketamine’s effect on the gating of auditory responses in the hippocampus of freely moving rats. Gating was measured by the ratio of the second-click response (P2) to the first-click response (P1), or P2/P1, with P1 and P2 measured as peak amplitudes. Ketamine (1, 3 or 6 mg/kg s.c.) dose- dependently increased P2/P1 ratio as compared to saline (s.c.). P2/P1 ratio in saline injected rats was 0.48 + 0.05 and was 0.73 + 0.17 in ketamine (3mg/kg) treated rats. Pre-inactivation of the medial septum with GABAA receptor agonist muscimol (0.25 μg/0.6 μL) or systemic administration of antipsychotic drugs, including chlorpromazine (5 mg/kg i.p.), haloperidol (1 mg/kg i.p.) or clozapine (7.5 mg/kg i.p.), decreased P2/P1 to values comparable to normal rats without drug injection. Infusion of muscimol in the medial septum or injection of antipsychotic drug alone did not affect the P2/P1 ratio. However, rats with selective lesion of the septohippocampal cholinergic neurons (by 192-IgG saporin) showed significant higher P2/P1 (0.86 + 0.10) than that of sham lesioned rats (0.26 + 0.07), but ketamine’s effect in increasing P2/P1 ratio was preserved. It is suggested that the septohippocampal cholinergic inputs participate in normal auditory gating in the hippocampus whereas the entire medial septum mediates ketamine-induced deficit of hippocampal auditory gating. In addition, the effectiveness of various antipsychotic drugs in antagonizing ketamine-induced impairment of auditory gating confirms the validity of this animal model of schizophrenia. (Supported by NSERC grant and CIHR grant 15685).

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

Li A-J, Dinh TT, Ritter S (2007) Destruction of NPY receptor expressing neurons in the arcuate nucleus causes obesity and hyperphagia without increasing lateral hypothalamic orexigenic peptide gene expression. Neuroscience 2007 Abstracts 524.20/BBB20. Society for Neuroscience, San Diego, CA.

Summary: NPY-SAP, a conjugate of neuropeptide Y (NPY) and the ribosomal inactivating toxin, saporin (SAP), is a compound that selectively lesions NPY receptor-expressing neurons. Previously we showed that injection of NPY-SAP into the hypothalamic arcuate nucleus (ARC) induces hyperphagia and obesity in rats. To further investigate the mechanisms responsible for NPY-SAP-induced obesity, we injected NPY-SAP or blank-saporin (B-SAP) control into the ARC and subsequently examined the expression of two orexigenic neuropeptide genes in the lateral hypothalamic area (LHA), which is densely innervated by ARC neurons. Our hypothesis was that loss of leptin-sensitive neurons in the ARC in the NPY-SAP injected rats would lead to increased expression of orexigenic neurons elsewhere in the hypothalamic feeding circuitry. Body weight gain and food intake were dramatically increased in the NPY-SAP group. In addition, expression of NPY and cocaine- and amphetamine-regulated transcript (CART) mRNA was significantly reduced in the ARC of obese rats, indicating a loss of NPY receptor-expressing NPY and CART neurons in this region. In contrast, NPY and CART gene expression in the dorsomedial hypothalamic nucleus was unchanged in NPY-SAP rats, indicating that the NPY-SAP-induced lesion was limited to the ARC. However, contrary to our hypothesis, expression of the orexigenic neuronpeptides, melanin-concentrating hormone (MCH) or prepro-orexin mRNA in LHA was not enhanced, but was slightly reduced in the NPY-SAP rats. These results indicate that an enhancement of MCH or orexin expression in the LHA is not necessary for the hyperphagia and obesity observed after NPY-SAP lesions in the ARC. Supported by PHS grant #DK 40498.

Related Products: NPY-SAP (Cat. #IT-28), Blank-SAP (Cat. #IT-21)