sfn2007

Rennie KE, Frechette M, Pappas BA (2007) Behavioural consequences of combined cholinergic lesion and chronic cerebral hypoperfusion in rats. Neuroscience 2007 Abstracts 698.16/R26. Society for Neuroscience, San Diego, CA.

Summary: Chronic cerebral hypoperfusion compromises the health of hippocampal neurons, leading to a slowly emerging loss of pyramidal cells accompanied by spatial memory impairments in rats. Recent research suggests that vascular abnormalities resulting in insufficient cerebral blood flow or impaired nutrient delivery to the brain represent a significant risk factor for Alzheimer’s disease (AD) and may contribute to its pathogenesis. AD is also characterized by dysfunction of the forebrain cholinergic system. Since there is evidence that this system is involved in the control of local cerebral blood flow, we hypothesized that there would be synergistic effects of chronic cerebral hypoperfusion and cholinergic dysfunction. Hence, the aim of this study was to determine whether cholinergic dysfunction exacerbates the effects of cerebral hypoperfusion. Female rats were subjected to forebrain cholinergic lesion or control surgery by intraventricular infusion of the immunotoxin 192-IgG-saporin (192S) or phosphate buffered saline (PBS) on postnatal day 7. Six months later the rats underwent permanent bilateral occlusion of the carotid arteries (2VO), which causes moderate, chronic cerebral hypoperfusion, or sham surgery. When exposed to an open field 48, 72 and 96 hours after 2VO or sham surgery, the groups did not differ on measures of overall activity. However, the cholinergic lesion increased the latency to enter the centre area, and reduced both the number of centre entries and the percentage of total distance that was traveled in the inner squares. The lesion effects were mainly seen in the combined 192S/2VO group while 192S or 2VO alone produced only minor behavioural changes. Elevated plus testing 2 weeks after surgery revealed a reduction in open but not closed arm entries due to the cholinergic lesion. Interestingly, the effects of 2VO were dependent on the status of the cholinergic system. 2VO increased open arm entries in the PBS group, but decreased this behaviour in the 192S group. Thus on both the open field and elevated plus maze, the cholinergic lesioned rats displayed more anxious behaviour, particularly after 2VO. Finally, cholinergic lesion produced impairments on the working memory version of the Morris water maze. Again, this effect was most pronounced in the combined 192S/2VO group. This effect is unlikely to be due to motivational or sensorimotor deficits as all groups performed similarly on a cued platform version of the maze. Cholinergic lesion and 2VO appear to act synergistically to produce behavioural alterations, even at relatively early time points after 2VO. Their combined effects on CA1 pyramidal cell viability are currently under examination.

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

Kalinchuk AV, Porkka-Heiskanen T, McCarley RW, Basheer R (2007) Progressive decrease in sleep deprivation-induced extracellular adenosine release and recovery NREM sleep following intracerebroventricular injection of 192 IgG-saporin. Neuroscience 2007 Abstracts 735.10/TT29. Society for Neuroscience, San Diego, CA.

Summary: The basal forebrain (BF) is an important site in the homeostatic regulation of sleep mediated by adenosine (AD) release (Porkka-Heiskanen et al., 1997). The BF comprises different neuronal populations, including cholinergic, GABAergic and glutamatergic cells. Immunotoxin 192 IgG-saporin has been used in several studies to investigate the role of the BF cholinergic vs. non-cholinergic cells in the regulation of spontaneous sleep and homeostatic sleep response after sleep deprivation (SD) but results of these studies are controversial. 2 weeks after local saporin injection into the caudal BF (horizontal diagonal band/magnocellular preoptic area/substantia innominata, HDB/MCPO/SI), recovery sleep is reduced; however, 2 weeks after ICV saporin injection, no changes in recovery sleep occur. We hypothesized that this difference in ICV vs. local effects might be explained by a delayed lesion of the cholinergic cells in the HDB/MCPO/SI area after ICV injection. Consequently, in the same rats, we examined the time course of the effects of ICV-injected saporin on SD-induced BF AD levels and the homeostatic sleep response at both 2 and 3 weeks post-injection. Male rats were ICV injected with saporin (6μg, n=9) or saline (n=5) and implanted with EEG/EMG electrodes and guide cannulae for microdialysis probes targeting the HDB/MCPO/SI. Experimental schedule, performed for each rat at 2 and 3 weeks post-injection, included spontaneous sleep-wake recording for 24h beginning at 8am (7am:7pm L:D) and SD for 6h beginning at 10am followed by recovery sleep at 4pm-8am. AD samples were collected at 30min intervals on SD day from 8am to 8pm. Histology evaluated the extent of cholinergic cell loss and probe locations. 2 weeks after ICV saporin injection, SD induced significant increases in BF AD levels (+126%), NREM recovery sleep duration (+41%) and NREM delta power (+91%). All values were similar to saline-treated animals. However, 3 weeks after ICV saporin injection, SD did not increase BF AD nor NREM recovery sleep, while delta power in NREM sleep had a modest increase (+21%). The changes observed 3 weeks after ICV injection were quantitatively similar to those observed 2 weeks after local BF saporin administration (Kalinchuk et al., 2005). We conclude that the effect of ICV saporin-induced cholinergic lesions follows a slower time course (3 weeks or longer) compared to local BF injections in reducing the SD-induced AD increase and the homeostatic sleep response. Taken together, our present and previous observations imply that cholinergic neurons in the BF play an important role in the regulation of SD-induced AD release and NREM recovery sleep.

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

Wood DA, Patterson N, Fuller P, Sherman D, Saper C, Lu J (2007) Genetic dissection of neural circuitry underlying REM sleep behavior disorder (RBD). Neuroscience 2007 Abstracts 736.28/VV11. Society for Neuroscience, San Diego, CA.

Summary: REM sleep behavior disorder (RBD), a parasomnia typically manifested as dream enactment behavior, may represent an early pathophysiologic manifestation of Lewy body diseases (LBD), such as Parkinson disease and dementia with Lewy bodies. Preclinical investigation of possible underlying neural mechanisms of RBD suggests that a set of glutamatergic neurons located in the sublaterodorsal nucleus (SLD), which project to GABA/glycine interneurons in the ventral horn are responsible for atonia during REM sleep (Lu et al. 2006, A putative flip-flop switch for control of REM sleep, Nature 441, 589-94). Based upon these findings, we hypothesize that a loss of glutamate from these neurons in the SLD produces REM sleep without atonia, an animal equivalent of RBD. To assess this question, we selectively eliminated glutamate release from SLD by injecting adeno-associated virus-Cre recombinase (AAV-Cre) into the SLD of mice with lox P sites flanking exon 2 of the vesicular glutamate transporter 2 (VGLUT2) gene. In addition, we examined the role of the ventromedial medulla (VMM) in REM atonia by injecting orexin-saporin in rats and AAV-Cre into flox-VGAT (vesicular GABA/glycine transporter) and flox-VGLUT2 mice. Consistent with our hypothesis, these data show that loss of the VGLUT2 gene in the SLD produces REM sleep without atonia (walking, running and myoclonic jerking) without alteration of total amount of REM sleep. Furthermore, loss of the VGLUT2 but not the VGAT gene in the intermediate VMM results in myoclonic jerking against the background of tonic atonia during REM sleep. Based upon these observations, we propose that suppression of muscle activity during REM sleep is controlled by the activation of excitatory glutamatergic projections from the SLD (with collaterals targeting the intermediate VMM) and from the intermediate VMM, which terminate at inhibitory interneurons in the spinal cord. Collectively, this work provides novel insight into the control of muscle tone during REM sleep, which may have implications for our understanding of neurological conditions that precede the onset of neurodegenerative disease.

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

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)

Haller J, Toth M, Zelena D, Halasz J (2007) Molecular basis of violent behavior: The role of NK1 receptors. Neuroscience 2007 Abstracts 531.22/GGG24. Society for Neuroscience, San Diego, CA.

Summary: Background. Neurons expressing Neurokinin1 receptor (NK1 or Substance P receptor) are abundant in limbic areas crucial for different emotional behaviors. In recent years, NK1 receptor blockers were proposed for the treatment of anxiety and depression. Moreover, in two different laboratory models, NK1 receptor blockade was successfully used to decrease violent components of aggression related behaviors in Wistar rats (Biol. Psychiatry, 2007, in press). In the above study, the NK1 receptor blockade reduced the number of more violent hard bites, while the number of soft bites was unaltered. Aggressive encounters were accompanied by a marked activation of neurons expressing NK1 receptors in the medial amygdala and in the hypothalamic attack area, where the highest number and proportion of activated NK1 positive neurons were found. Aim / Methods. We evaluated the precise role of neurons expressing NK1 receptors in the hypothalamic attack area during resident/intruder test. These neurons were selectively eliminated by a Substance P conjugated saporin bilateral microinjection into the hypothalamic attack area. After a week recovery, lesioned and vehicle treated control residents were faced with a smaller untreated opponent in their home cages for 20 min. The brains of the residents were later removed to assess the site of injection and the extent of the lesion. Results. In lesioned Wistars, the bilateral microinjection resulted in a complete and selective disruption of NK1 positive neurons in the hypothalamic attack area. Compared to vehicle injected controls, the number of hard bites toward unfamiliar residents showed a marked decrease (almost a complete abolition) in the lesioned group. The latency of hard bites was significantly increased compared to vehicle injected controls. The number of bite attacks was also reduced, but this reduction was mainly secondary to the dramatic reduction in the number of hard bites. Conclusions. Our data show that hypothalamic neurons expressing NK1 receptors are involved in the control of aggressiveness, especially in the expression of violent attacks. These data confirm and support earlier results that NK1 antagonists – beyond anxiety and depression – may also be useful in the treatment of aggressiveness and violence.

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

Gaffan D, Baxter MG, Browning PGF (2007) Intact delayed nonmatching-to-sample in monkeys with combined lesions of the temporal cortical cholinergic system and the fornix. Neuroscience 2007 Abstracts 341.11. Society for Neuroscience, San Diego, CA.

Summary: Rhesus monkeys were pre-operatively trained in truly trial-unique delayed nonmatching-to-sample (DNMS) in an automated apparatus. They were then divided into a control group (n=3) and an experimental group (n=3) and received injections into the inferior temporal cortex of either saline (controls) or the selective cholinergic immunotoxin ME20.4-saporin (experimentals). A postoperative DNMS test showed no significant impairment in the experimental group, both groups performing at their pre-operative level. Both groups then underwent a second surgery to transect the fornix. Again, there was no significant impairment in DNMS, both groups performing at their pre-operative level. If the lesions are confirmed histologically then these results are in marked contrast to our findings with scene learning, in which monkeys with the same combined lesion as those in the present experimental group were severely impaired. However, a number of recent studies have shown that tasks with temporally complex events extended over trials, like DNMS, discrimination learning set, and serial reversal set, depend on a short-term prospective memory strategy that is supported by the interaction of temporal cortex with prefrontal cortex. Thus, the performance of DNMS does not require the laying down of new long-term memories.

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

Browning PG, Gaffan D, Baxter MG (2007) Severe visual learning impairments in monkeys with combined but not separate lesions of the temporal cortical cholinergic system and the fornix. Neuroscience 2007 Abstracts 341.7. Society for Neuroscience, San Diego, CA.

Summary: A dense amnesia can be produced in the monkey by sectioning the anterior temporal stem, amygdala and fornix, a procedure which deafferents temporal cortex from modulatory inputs from the midbrain and basal forebrain. The present experiment investigated the neurochemical specificity of these severe learning impairments by selectively destroying cholinergic projections to the entire inferior temporal cortex by making multiple injections of the immunotoxin ME20.4-saporin into the inferior temporal cortex bilaterally. Six male macaque monkeys were preoperatively trained to learn new object-in-place discrimination problems each day until they could rapidly learn many such problems within a testing session. The monkeys then underwent surgery and received either injections of immunotoxin (n=3) or injections of saline (n=3). Both groups of monkeys were unimpaired when postoperative and preoperative performance were compared. Each monkey then underwent a second surgery to transect the fornix. After this surgery monkeys who had previously received injections of immunotoxin into temporal cortex showed a severe learning impairment, whereas monkeys who had previously received injections of saline showed a mild impairment. Monkeys with the combined immunotoxin plus fornix lesion were also severely impaired at concurrent object discrimination learning. These results suggest that different neuromodulatory inputs to inferior temporal cortex may act in concert to support cortical plasticity in visual learning such that the loss of acetylcholine only is not sufficient to disrupt normal learning behavior. The results also suggest that in monkeys, as in humans with Alzheimer’s disease, severe memory impairments occur only when a loss of acetylcholine projections to cortex is accompanied by organic tissue damage.

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

Baxter MG, Kyriazis DA, Croxson PL (2007) Cholinergic depletion of prefrontal cortex does not impair episodic memory or strategy implementation in rhesus monkeys. Neuroscience 2007 Abstracts 341.9. Society for Neuroscience, San Diego, CA.

Summary: The prefrontal cortex is involved in regulating multiple aspects of memory, decision-making, and cognitive control. Cholinergic input to prefrontal cortex is thought to be involved in supporting its functions. To examine this hypothesis we tested 4 rhesus monkeys (3 male) with cholinergic depletion of ventrolateral prefrontal cortex (N=2) or the entire prefrontal cortex, excluding its medial aspect (N=2). Selective cholinergic depletion was produced by multiple injections of the immunotoxin ME20.4-saporin (0.02 ug/ul) into the prefrontal cortex. These monkeys were tested on two tasks that each require frontal-inferotemporal interaction, as well as an intact ventrolateral prefrontal cortex. The first, strategy implementation, requires monkeys to apply different choice strategies to different categories of objects in order to maximize the rate of reward delivery, and engages decision-making and cognitive control. The second, scene memory, is a test of episodic memory in which monkeys rapidly learn 20 new object-in-place scene discrimination problems within a single test session. Cholinergic depletions of prefrontal cortex, whether they were limited to ventrolateral prefrontal cortex or included the whole of lateral and orbital prefrontal cortex, were without effect on either strategy implementation or new scene learning relative to each monkey’s preoperative performance. Thus, episodic memory and strategy implementation can proceed normally even with severely disrupted cholinergic input, so loss of cholinergic input on its own cannot explain impaired prefrontal function in conditions such as Alzheimer’s disease. Acetylcholine may work in tandem with other neuromodulators to affect prefrontal cortex function; alternatively, it may only be involved in very specific aspects of cortical function, for example representational plasticity.

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