References

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.

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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.

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Gompf HS, Fuller PM, Saper CB, Lu J (2007) Locus coeruleus (LC) is involved in sustaining arousal. Neuroscience 2007 Abstracts 736.3/UU16. Society for Neuroscience, San Diego, CA.

Summary: The locus coeruleus (LC) has traditionally been thought to be involved in arousal; however, lesions of the LC have minimal effects on basal sleep-wake behavior. We propose that the LC instead may be required to sustain arousal under conditions of environmental challenge. To test this hypothesis, we intraventricularly injected saline, or 0.25, 0.5, or 1µg anti-DBH-saporin (DBH-SAP selectively lesions the LC), and implanted EEG/EMG electrodes. On recording days, each animal was paired with a normal rat (social interaction) and presented with novel objects every hour for 5 hours from ZT 6 to ZT 11. We then repeated the same experiment for 2.5 hrs and immunostained tissue for Fos and TH or Fos and DBH. We also repeated the same experiment in rats with unilateral LC lesion by 6-OHDA. During 5 hr of stimulation with novel objects and social interaction (distracting stimuli, DS), controls or partial LC lesioned animals (0.25 µg DBH-SAP) spent 83 ± 8% and 92 ± 4% awake respectively (n = 3 and 4, p = 0.4) whereas animals with complete LC lesions (0.5 and 1 µg) spent significantly less time in wakefulness (59 ± 4% and 66 ± 5% respectively, n = 3 and 4, p = 0.0005). The reduction of wakefulness occurred primarily during the second 30 mins of each hour. Following DS exposure, Fos was highly expressed in the cerebral cortex in both LC lesioned groups and controls. Furthermore, we found a correlation (R2 = 0.79) between the remaining LC neurons and wakefulness under DS. Rats with loss of one LC showed no changes in wakefulness, and Fos was highly and symmetrically induced in the cerebral cortex. Our results suggest that the LC is specifically involved in sustaining arousal.

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Martin MM, Carter LA, Jones JL, Winter SS, Wallace DG (2007) Organization of food protection behavior is differentially influenced by hippocampal and cortical cholinergic deafferentation. Neuroscience 2007 Abstracts 742.6/AAA9. Society for Neuroscience, San Diego, CA.

Summary: Previous work has suggested that rats use temporal information to organize their food protection behaviors. Studies have demonstrated different roles for hippocampal and cortical cholinergic function in processing of temporal information in standard interval timing procedures. The present study examined the role of hippocampal and cortical cholinergic function on the organization of food protection behavior. Long Evans female rats received either injections of 192 IgG-Saporin (SAP) or saline (SHAM) into the medial septum (MS) or nucleus basalis (NB). Subsequent to recovery, rats were placed into an enclosure and provided a hazelnut in the presence of an unoperated conspecific. All rats engaged in dodging or bracing behaviors to prevent the theft of the hazelnut. During a dodge, the rat places the food item in its mouth to use both fore- and hind-limbs to escape the approaching conspecific. In contrast, during a brace, the rat’s forelimbs maintain contact with the food item, and only the hind limbs are used to make shorter lateral movements. Only rats receiving sham lesions displayed a consistent transition from primarily engaging in dodging behavior to primarily engaging in bracing behavior during the consumption of the hazelnut. The MS SAP group displayed a disruption in their temporal organization of food protection behaviors. Although the NB SAP animals displayed impaired responding to the approaching conspecific (resulting in frequent thefts), their food protection behaviors tended to exhibit temporal organization. These results provide further evidence as to the role of the basal forebrain cholinergic system in temporal organization of behavior.

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Wallace DG, Knapp SK, Silver JA, Martin MM, Winter SS (2007) Selective hippocampal cholinergic deafferentation disrupts exploratory trip organization. Neuroscience 2007 Abstracts 743.17/BBB11. Society for Neuroscience, San Diego, CA.

Summary: Rats organize their exploration of an environment around a central location or home base. Movements away from the home base are characterized as a series of slow progressions punctuated by stops. Subsequent to the last stop, the homeward segment is a single, rapid progression associated with a consistent temporal pacing of linear speeds. Observing these characteristics of exploratory behavior independent of environmental cue availability or familiarity has supported rats’ use of self-movement cues generated after departing the home base to estimate the distance and direction back to the home base. The current study investigated the effects of selective hippocampal cholinergic deafferentation on home base establishment and exploratory trip organization. Long Evans female rats either received injections of 192 IgG-Saporin (SAP) or saline (SHAM) into the medial septum. Subsequent to recovery, rats were placed on a large circular table with access to a refuge under complete dark conditions (infrared cameras and goggles were used to visualize the rat). Although all rats established a home base in the refuge, impairments in exploratory trip organization specific to the homeward segment were observed in SAP rats. Specifically, SAP rats displayed inconsistent temporal pacing of homeward segment linear speeds. These observations are consistent with a role for hippocampal cholinergic function in processing self-movement cues.

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Young D, Howe WM, Martinez V, Bruno JP, Sarter M (2007) Neuronal mechanisms underlying the cognitive symptoms in a model of schizophrenia: prefrontal cholinergic inputs are necessary for attentional performance following repeated exposure to amphetamine. Neuroscience 2007 Abstracts 606.9/GG1. Society for Neuroscience, San Diego, CA.

Summary: The neuronal and cognitive effects of repeated exposure to amphetamine (AMPH) model important aspects of schizophrenia. Our prior results indicated that the attentional performance of AMPH-pretreated animals was maintained by abnormally high levels of prefrontal acetylcholine (ACh) release, and that the disruption of attentional performance by AMPH challenges was associated with a failure of the prefrontal cholinergic input system to respond to task onset (Kozak et al. 2007). The present experiment was designed to demonstrate that prefrontal cholinergic inputs are necessary for the (residual) attentional performance following repeated AMPH exposure. As removal of cortical cholinergic inputs per se disrupts attentional performance, we tested the hypothesis that limited prefrontal cholinergic deafferentation, which does not affect baseline attentional performance, prevents the establishment of normal performance following AMPH pretreatment. Rats were trained to perform a sustained attention task requiring the detection of visual signals and the discrimination between signal and non-signal events. Bilateral infusions of small concentrations and volumes of the immunotoxin 192 IgG-saporin into the medial prefrontal cortex did not affect the animals’ baseline performance. After re-establishing stable baseline performance, animals were pretreated with either saline or AMPH in accordance with an established, non-neurotoxic, escalating dosing regimen (1-10 mg/kg, twice daily over 40 days; Robinson et al. 1988). Animals were tested daily throughout the experiment. Following completion of the pretreatment regimen, the attentional performance of sham-lesioned controls recovered slowly over three weeks of continued training/testing. In contrast, performance recovery of deafferented, AMPH-pretreated animals was robustly attenuated and failed to reach pre-treatment levels. Collectively, these results indicate the necessary role of the prefrontal cholinergic input system in mediating the residual attentional performance of repeated AMPH. Therefore, pro-cholinergic treatments are predicted to benefit the attentional performance of schizophrenics. Repeated AMPH serves as a useful model to investigate the neuronal mechanisms underlying the cognitive symptoms of schizophrenia.

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Ganapini V, Powers F, Kuper K, Taylor A, Fraley GS (2007) Galanin-like peptide stimulates feeding and sexual behavior via dopaminergic fibers within the medial preoptic area of adult male rats. Neuroscience 2007 Abstracts 626.14/VV17. Society for Neuroscience, San Diego, CA.

Summary: Galanin-like peptide (GALP) is a hypothalamic neuropeptide known to regulate both food intake and sexual behaviors in adult male rats. We have demonstrated that ICV GALP administration elicits a significant fos response within the mPOA; thus, we feel that GALP stimulates feeding and reproduction by actions within the mPOA. Recent data from our and other labs have led us to suspect that GALP effects on these behaviors are due to activation of tuberoinfundibular dopaminergic neurons that terminate within the mPOA. To test the hypothesis that GALP activates mPOA dopaminergic systems, we utilized an immunolesion technique to eliminate dopaminergic fiber input specific to the mPOA via a dopamine-transporter specific toxin (DATSAP, n = 8) and compared to control injections (SAP, n = 8). All animals were sexually experienced adult male Long Evans rats. We first tested their response to a sexually-primed female rat. DATSAP-treated male rats showed a significant (p <0.001) reduction in male sexual behavior compared to SAP controls. We found that elimination of dopamine fibers within the mPOA significantly (p < 0.001) eliminated all aspects of male sexual behavior under normal mating paradigms. Injections of GALP (5.0 nmol) significantly increased (p < 0.01) male sex behavior in SAP control male rats but GALP was unable to stimulate the expression of these behaviors in DATSAP-treated rats. ICV GALP significantly (p < 0.05) stimulated fos within the mPOA of SAP rats but not in DATSAP-treated male rats. There was no significant difference in 24 hr food intake between SAP and DATSAP rats. However, the orexigenic effect of ICV GALP was significantly (p < 0.001) attenuated in DATSAP-treated male rats compared to SAP controls. These data suggest that GALP activates feeding and sexual behaviors in male rats by stimulating dopaminergic neurons that terminate within the mPOA.

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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.

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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.

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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.

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