sfn2003

Fitz NF, Gibbs RB, Johnson DA (2003) Arousal enhances delayed match to position T-maze performance independent of septo-hippocampal cholinergic projections. Neuroscience 2003 Abstracts 425.17. Society for Neuroscience, New Orleans, LA.

Summary: Infusion of the selective cholinergic immunotoxin, 192 IgG-saporin (SAP) into the medial septum (MS) of rats selectively lesions cholinergic neurons projecting to the hippocampus and impairs acquisition of a delayed matching to position (DMP) T-maze task. The intent of the present study was to determine if enhanced performance associated with arousal is dependent on septo-hippocampal cholinergic projections. Male Sprague-Dawley rats received MS infusions of SAP 0.22 µg in 1µl or vehicle. Fourteen days later, animals were trained on the DMP spatial memory task. SAP and control animals were randomized into an “arousal” group that was injected with saline (IP; 1 ml/Kg) 30 min before testing each day or a “non-arousal” group that was not. SAP lesions significantly impaired acquisition of the DMP task in both the arousal and non-arousal groups. Conversely, arousal significantly enhanced acquisition in both control and SAP lesioned rats. There was no significant interaction between the effects of cholinergic lesions and arousal. These results suggest that septo-hippocampal cholinergic projections are not engaged in enhanced spatial learning mediated by arousal.

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McGaughy JA, Jindal M, Eichenbaum HB, Hasselmo ME (2003) Cholinergic deafferentation of the entorhinal cortex in rats impairs encoding of novel but not familiar stimuli in a delayed non-match to sample task (DNMS). Neuroscience 2003 Abstracts 425.4. Society for Neuroscience, New Orleans, LA.

Summary: Muscarinic cholinergic receptor activation in entorhinal cortex (EC) activates intrinsic depolarizing membrane currents which cause self-sustained spiking activity in single neurons (Klink and Alonso, J. Neurophys. 77, 1997). This effect may underlie delay activity and match-dependent activity changes in delayed match to sample tasks (Fransen et al., J. Neurosci. 22, 2002) and could allow accurate maintenance of novel information without dependence on synaptic modification associated with previous exposure (familiarization). Consistent with this, research in human subjects suggest that the medial temporal lobes are specifically activated during working memory for novel but not familiar stimuli (Stern, et al. Hippocampus v. 11, 2001), and cholinergic deafferentation of the rhinal cortex in non-human primates has been shown to impair memory for trial-unique (novel) stimuli (Turchi et al., SFN abstracts v. 28). The current study tests the hypothesis that cholinergic deafferentation of the EC produces impairments in working memory for novel but not familiar stimuli. Prior to surgery rats were trained in an odor DNMS task with a brief delay. After reaching asymptotic performance, rats were infused with either 192-IgG-saporin (SAP) or its vehicle into the EC (0.01 µg/µl; 1.0 µl/injection; 6 infusions/hemisphere). Rats were not impaired at any delay when tested with familiar odors but showed significant, persistent impairments when tested with novel odors. An increase in task difficulty alone was insufficient to explain these effects. These data support the hypothesis that cholinergic afferents to the EC activate cellular mechanisms of sustained spiking activity necessary for maintenance of novel but not familiar stimuli in a working memory task. Support Contributed By: NIH MH61492, MH60013, DA16454.

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Butt AE, Corley S, Cabrera S, Chavez C, Kitto M, Ochetti D, Renovato A, Salley T, Sarpong A (2003) 192 IgG-saporin lesions of the nucleus basalis magnocellularis in rats fail to disrupt acquisition or retention of differential reinforcement of low rate responding. Neuroscience 2003 Abstracts 425.5. Society for Neuroscience, New Orleans, LA.

Summary: The frontal cortex has been implicated in supporting timing behavior in tests of differential reinforcement of low rate responding (DRL) in rats. DRL performance is similarly influenced by anticholinergic drugs; scopolamine interferes with DRL performance by increasing the number of nonreinforced responses and thus decreasing DRL efficiency. Because the frontal cortex receives significant cholinergic input from the nucleus basalis magnocellularis (NBM) in rats, we hypothesized that NBM lesions would disrupt DRL performance in the current experiment. Male Long-Evans rats were placed first in a DRL 10 s schedule of reinforcement before advancing to a DRL 20 s schedule. Rats received 50 trials per day for 20 consecutive days on both DRL schedules. When rats reached stable performance, they received either bilateral 192 IgG-saporin lesions of the NBM or sham lesions. Upon recovery, rats were reintroduced to the DRL 20 s task for 10 days of post-operative testing. Finally, rats were tested using a novel delay interval in a DRL 30 s task. Testing continued for 10 additional days. Results showed that the NBM lesion group showed no significant change in either the total number of responses or in DRL efficiency (reinforced responses / total responses) between pre- and post-operative DRL 20 s testing. Subsequent acquisition in the DRL 30 s task was similarly not disrupted by NBM lesions. The effectiveness of the lesions was verified by acetylcholinesterase (AChE) staining, which showed pronounced depletion of cortical AChE with normal AChE-positive staining in the hippocampus and medial septal area. These data suggest that the NBM is not critically involved in either the acquisition or retention of DRL performance.

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

Fletcher BR, Baxter MG, Rapp PR, Shapiro ML (2003) 192-IgG saporin lesions of the medial septum and vertical diagonal band impair cognitive flexibility. Neuroscience 2003 Abstracts 425.8. Society for Neuroscience, New Orleans, LA.

Summary: Learning and memory remain largely intact following selective basal forebrain cholinergic lesions. By comparison, single unit recording studies have documented reliable effects of such lesions, including abnormally rigid hippocampal place fields when animals are confronted with changes in the configuration of the testing environment. The present experiment tested the prediction that cholinergic lesions of the basal forebrain would impair performance of tasks requiring cognitive flexibility. Rats received 192-IgG saporin or control vehicle injections into the medial septal nucleus and vertical diagonal band, and were tested on cued and spatial delayed match-to-place tasks in a radial arm water maze. Test sessions consisted of four sample trials in which animals searched for a cued or hidden escape platform located in a fixed position at the end of one arm (60 sec cutoff, inter-trial interval = 15 sec). A memory delay was imposed by returning rats to the home cage for a variable delay (15 sec. – 6 hrs), followed by two test trials. The lesion and control groups learned at similar rates in both versions of the task, and performed comparably on the critical test trials, independent of the length of the retention interval. However, lesioned rats were impaired during the transition from the cued to spatial variants of testing. Specifically, the lesion group made significantly more errors on an early sample trial in the spatial task, returning to the location that was previously correct during cued training. Pending histological confirmation of the extent and selectivity of the experimental lesions, this pattern of results suggests that damage to the basal forebrain cholinergic system spares spatial learning but impairs cognitive flexibility when task contingencies are changed.

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

Nelson LE, Franks NP, Maze M (2003) Discrete lesioning of orexin (hypocretin)-containing neurons potentiates dexmedetomidine- but not pentobarbital-induced hypnosis. Neuroscience 2003 Abstracts 426.13. Society for Neuroscience, New Orleans, LA.

Summary: Introduction: Recent work suggests that anesthetics putatively modulated by the α2-adrenoceptor (e.g. dexmedetomidine (DEX)) or the GABAA receptor (e.g. pentobarbital (PTB)) elevate and depress c-Fos expression, respectively, in the orexinergic perifornical area (PeF)1. Here the hypnotic effects of DEX and PTB are assessed after selective lesion of the PeF by orexin-B conjugated to saporin (OX-SAP). Methodology: Anesthetized Fischer rats were administered stereotaxic PeF injections of saline (0.5µl/side) or OX-SAP (490ng/0.5μl/side; as described2). Loss of righting reflex (LORR) induced by DEX (150μg/kg, SC), PTB (50mg/kg, SC), and saline was tested 1 day pre- and 1, 4, 8, and 12 days post-surgery, then lesions were assessed histologically. All data are presented as means±SEMs (n=6; comparisons by unpaired t-tests and ANOVA, Newman-Keuls). Results: Bilateral PeF lesions enhanced DEX-induced hypnosis at days 8 (281.2±15.8 min; p<0.05) and 12 (322.7±15.93 min; p<0.001) as compared to naïve (234.5±9.0 min) and saline sham animals (day 8, 236.7±9.8 min; day 12, 242.8±10.80 min). In contrast, PTB-induced LORR remained unaffected at day 12 (124.8±6.8 min) relative to naïve (119.4±4.6 min) and sham (120.8±5.3 min). These results agree with previous reports that by day 12, PeF-microinjected OX-SAP induces roughly 80% cell loss2. Conclusion: The absence of a functional PeF potentiates hypnosis induced by DEX but not PTB, as perturbation of the PeF by microinjected GABAA receptor antagonist gabazine is known to 1. References: 1 Nelson et al. (2002) SfN abstract 776.14/M20; 2 Geraschenko et al. (2001) J Neurosci 21:7273-83.

Related Products: OX7-SAP (Cat. #IT-02)

Kline IV RH, Wiley RG (2003) SSP-saporin decreases formalin induced c-Fos expression throughout the dorsal horn. Neuroscience 2003 Abstracts 174.7. Society for Neuroscience, New Orleans, LA.

Summary: Substance P (SP) antagonists and SP-saporin have been shown to decrease phase II of the formalin test suggesting an important role for SP in this model of persistent pain. SP antagonists also decrease formalin induced c-fos expression in dorsal horn neurons. A congener of SP-sap that is more stable and has higher affinity for NK-1R, SSP-sap (Sar9Met(02)11-substance P-saporin) has been studied by injection into the striatum and hippocampus where it was more potent and specific than SP-sap. In the present study, this selective and more potent toxin was used to determine the effects of destroying dorsal horn NK-1R on behavior and c-fos induction after intraplantar formalin. Twelve Sprague Dawley male rats were injected intrathecally with 100ng SSP-sap or PBS. After 2 weeks survival, rats underwent hindpaw formalin injections and behavioral scoring, and then were sacrificed after 3 hours and the lumbar spinal cords processed for immunohistochemical demonstration of NK-1R and c-fos. There were significant correlations between the loss of superficial laminae NK-1R neurons, decreased formalin behavior and dorsal horn c-fos expression. Therefore lumbar i.t. SSP-sap 1) decreased NK-1R cells in laminae I but not in the deeper laminae 2) decreased phase II formalin behavior 3) decreased c-fos in both the superficial and deep laminae. Since c-fos expression in the deeper laminae was decreased and NK-1R was spared in these laminae, we conclude that a lesion affecting only laminae I NK-1R lesion alters activation of neurons throughout the dorsal horn suggesting a key role for the missing neurons in the transfer of nociceptive inputs to deeper laminae.

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Xie Y, Vanderah TW, Ossipov MH, Lai J, Porreca F (2003) A single rostral ventromedial medulla (RVM) treatment with cholecystokinin-saporin (CCK-sap) prevents the development of opioid-induced paradoxical pain and spinal morphine antinociceptive tolerance. Neuroscience 2003 Abstracts 177.4. Society for Neuroscience, New Orleans, LA.

Summary: Sustained morphine elicits tactile and thermal hypersensitivity (opioid-induced paradoxical pain) and antinociceptive tolerance which are mediated through the time-dependent activation of descending facilitation from the RVM. With morphine exposure, CCK expression and/or release may be altered to activate pain facilitatory neurons of the RVM, manifesting as diminished spinal morphine antinociception (antinociceptive tolerance). To explore a possible role of RVM CCK in morphine-induced paradoxical pain and tolerance, CCK-SAP conjugate was used to selectively lesioned RVM neurons expressing CCK receptors. Male S-D rats received a single RVM injection of CCK, SAP or CCK-SAP. Behavioral responses to tactile (von Frey) and thermal (radiant heat) stimuli were normal 3,7,14 and 28 days after injection. RVM CCK microinjection produced tactile and thermal hypersensitivity in uninjured rats 28 days after receiving RVM CCK or SAP, but not in those receiving CCK-SAP, suggesting the probable loss of RVM CCK receptor-expressing cells. 28 days after RVM CCK, SAP or CCK-SAP injections, rats were implanted with placebo or morphine pellets. Morphine pelleted rats pretreated with RVM CCK or SAP developed tactile and thermal hypersensitivity and spinal antinociceptive tolerance. In contrast, animals pretreated with RVM CCK-SAP did not show morphine induced tactile or thermal hypersensitivity and antinociceptive tolerance was not present. Moreover, CCK-SAP, but not CCK or SAP, pretreatment significantly attenuated the antinociceptive effect of RVM morphine. This suggests that RVM CCK activates tonic descending facilitation driving morphine-induced abnormal pain and spinal antinociceptive tolerance. Moreover, these results suggest the possibility that CCK and opioid receptors may colocalize on some RVM neurons which may act to facilitate pain transmission.

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Harasawa I, Lai J, Porreca F, Fields HL, Meng ID (2003) Selective elimination of mu-opioid receptor expressing neurons in the rostral ventromedial medulla (RVM) does not affect periaqueductal gray (pag) stimulation-produced analgesia. Neuroscience 2003 Abstracts 177.5. Society for Neuroscience, New Orleans, LA.

Summary: PAG stimulation produces antinociception at spinal levels by modulating RVM neuronal activity. Microinjection of saporin conjugated with the mu-opioid receptor agonist dermorphin (DERM-SAP) into the RVM selectively eliminates MOR expressing neurons and diminishes neuropathic pain symptoms (Porreca et al., 2001). The aim of the present study was to determine whether MOR expressing neurons in the RVM are required for PAG stimulation produced analgesia (PAG/SPA). The minimum electrical current required to inhibit the tail flick response was compared in barbiturate-anesthetized rats given a single RVM injection of SAP or DERM-SAP 3-4 weeks prior to testing. Thresholds in SAP and DERM-SAP treated rats were not different. Furthermore, microinjection of the glutamate receptor antagonist kynurenic acid (10 mM, 800 nl) into the RVM disrupted PAG/SPA in both SAP and DERM-SAP treated rats. These results indicate that 1) mu-receptor expressing neurons in the RVM are not necessary for PAG/SPA, and 2) excitatory amino acid transmission in the RVM is critical for PAG/SPA. In additional experiments, inhibition of neurotransmitter release in the RVM by the microinjection of cobalt chloride (CoCl2, 100 mM, 800 nl), produced significant antinociception only in DERM-SAP treated rats. This finding suggests that DERM-SAP injections result in increased tonic inhibition of RVM neurons and that CoCl2 disinhibits these neurons to produce antinociception. Tonic inhibition of off-cells would account for our failure to find off-cells in DERM-SAP treated rats.

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Leung LS, Shen B, Ma J, Rajakumar N (2003) Cholinergic activity enhances hippocampal CA1 long-term potentiation during walking in rats. Neuroscience 2003 Abstracts 255.5. Society for Neuroscience, New Orleans, LA.

Summary: Long-term potentiation (LTP) at the basal dendrites of CA1 pyramidal cells was induced by a single 200-Hz stimulation train (0.5-1 sec duration) in freely behaving rats during one of four behavioral states – awake-immobility (IMM), walking, slow-wave sleep (SWS) and rapid-eye-movement sleep (REMS). Field excitatory postsynaptic potentials (fEPSPs) generated by basal dendritic excitation of CA1 were recorded before and up to 20 hours after the tetanus. Following a tetanus during any behavioral state, basal dendritic LTP was > 170% of the baseline for the first 30 min after the tetanus and decayed to ~125% at 20 hours after. LTP induced during walking was significantly larger than that induced during IMM, SWS or REMS. LTP induced during IMM, SWS and REMS was not significantly different from each other. To test the hypothesis that septohippocampal cholinergic activity enhanced LTP during walking than during immobility, rats were either pretreated with muscarinic cholinergic antagonist scopolamine (5 mg/kg i.p.) or given selective cholinotoxin IgG192-saporin in the medial septum. Pretreatment with scopolamine decreased the LTP induced during walking but did not affect that induced during IMM, such that the difference between LTP induced during walking and IMM was abolished. In IgG192-saporin injected rats, there was no difference in the LTP induced during walking and during IMM, and scopolamine did not reduce the LTP induced during walking. In contrast, sham-lesioned rats, like other control rats, showed larger LTP induced during walking than during IMM, and LTP induced during walking was attenuated by scopolamine. This appears to be the first demonstration of an enhancement of hippocampal LTP by physiologically activated septal cholinergic inputs. LTP of the CA3 to CA1 synapses may serve important behavioral functions.

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Muir JL, Harrison FE (2003) H3 receptor antagonists modulate behaviour in a visual spatial attention task in rats with selective lesions of the nucleus basalis magnocellularis. Neuroscience 2003 Abstracts 296.7. Society for Neuroscience, New Orleans, LA.

Summary: It is well known that the cholinergic system suffers a large amount of damage in Alzheimer’s Disease (AD). The histaminergic system is known to interact with the cholinergic system but is thought to be largely spared in AD. Compounds which affect histaminergic transmission therefore offer a new further therapeutic avenue to be considered. The effects of two selective H3 receptor antagonists, Thioperamide (1.0, 3.0, 10.0mg/kg) and Ciproxifan (1.5, 3.0, 5.0mg/kg), were investigated for their ability to modulate visual spatial attention using the Five Choice Serial Reaction Time Task. The animal model used was that of cholinergic lesions of the nucleus basalis Magnocellularis (nbM) in the basal forebrain using the selective immunotoxin IgG Saporin. Thioperamide, without affecting overall accuracy, showed very strong trends towards a reduction in anticipatory responses in both sham and lesion groups and also showed a slight reduction in perseverative responses. The more potent Ciproxifan showed no overall change in accuracy but led to a reduction in the anticipatory responses in nbM lesioned animals at all three doses of the drug, returning them to equivalent levels of responses to the sham group. This effect was independent of any overall decrease in activity levels as there were no concomitant changes in response latencies or number of trials completed. Hence these pharmacological manipulations reduced the levels of impulse behaviours manifest by lesioned animals.

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