References

Carter ES, Newman LA, Mcgaughy J (2009) Effect of aging and prefrontal cholinergic deafferentation on working memory for familiar and novel odors. Neuroscience 2009 Abstracts 879.14/EE124. Society for Neuroscience, Chicago, IL.

Summary: Aging is associated with cholinergic fiber loss in the entorhinal cortex (EC). Previous research has shown that acetylcholine (ACh) in this region mediates memory for novel information (Schon et al., 2005), and cholinergic lesions of the EC in young rats impair memory for novel, but not familiar, stimuli at an odor delayed non-match to sample task (DNMS; McGaughy et al., 2005). Currently, we tested whether age-related cholinergic fiber loss in the medial EC of male rats would be sufficient to produce impairments in memory for novel information during the DNMS task. Half of the aged animals were subjected to cholinergic depletion of medial, prefrontal cortex (pACh-lx) including both prelimbic and anterior cingulate cortex prior to the onset of testing. We hypothesized that this previous damage would result in impairments in memory for familiar items and would prevent improvements in memory shown after repeated exposure to novel items. Additionally the effects of increasing the delay between sample and choice portions of the test and memory for list of items were assessed. The pACh-lx animals were not impaired relative to sham-lx animals at memory for familiar information when there was a minimal delay between the sample and choice. However if a 15 minute delay was introduced between the sample and choice phase, pACh-lx rats performed more poorly than sham-lx rats. This suggests that ACh in the medial, prefrontal cortex is necessary for maintaining representations of familiar stimuli over a delay period. Aged rats showed accuracy impairments during sessions that required encoding of novel samples relative to their own performance at sessions requiring encoding of familiar samples. This impairment was greater on trials that required rats to discriminate the novel sample from a familiar non-match than on trials where all stimuli were novel. Though the extent of cholinergic fiber loss in EC due to aging was highly similar to that produced by infusion of the 192 IgG saporin to the EC of young rats, the severity of the cognitive impairments due to aging was not as great as that produced by lesioning. These data suggest that impact of damage to the cholinergic fibers of EC may vary based on whether the deterioration is gradual or has an acute onset.

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Bailey AM, Enos J, Medley V (2009) Damage to nucleus basalis magnocellularis (nBM) cholinergic target areas produce different effects on the acquisition of learning set. Neuroscience 2009 Abstracts 879.15/EE125. Society for Neuroscience, Chicago, IL.

Summary: Lesions to the nucleus basalis magnocellularis (nBM) using either quisqualic acid or 192 IgG-saporin produce differing effects on the acquisition of learning set. Specifically, quisqualic acid lesions produce severe and long lasting impairments but 192 IgG-saporin lesions produce transient effects on learning set acquisition. One possible explanation for acquisition differences involves altered neuronal activity in the cholinergic target areas of the nBM. We examined two main cholinergic targets of the nBM, namely the amygdala and the prefrontal cortex (PFC). Rats with either NMDA (20 µg/µl) lesions to the basolateral amygdala (n=10) or NMDA (20 µg/µl) lesions to the anterior cingulate PFC (n=6) were tested on an olfactory learning set formation task as well as operant delayed non-matching to-position (DNMTP) and open field activity. The rats with amygdala lesions were additionally tested on a fear conditioning task. Lesions to the PFC significantly impaired acquisition of learning set as measured by chance performance on Trial 2 (M = 56.17%, SD = 7.47). Rats with PFC lesions did not differ from sham animals on the DNMTP task (p > .05) or in activity counts in an open field (p > .05). However, rats with NMDA lesions to the amygdala were significantly higher than chance (50% correct) on Trial 2 (p .05) or percentage correct on the DNMTP task (p > .05). NMDA lesions to the amygdala did, however, significantly decrease time spent freezing to an aversive CS+ in the fear conditioning task (p < .05). In total, the results imply that learning set acquisition differences following either quisqualic acid or 192 IgG-saporin lesions to the nBM are not likely due to damage to the cholinergic projection to the amygdala but may be associated with altered PFC activity.

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Hernandez MA, Pineda JB, Del Valle-Mondragón L, Alcaraz-Zubeldia M, Ríos C, Pérez-Severiano F (2009) Evaluation of the effect of molsidomine on nitregic system in an experimental model of cognitive impairment. Neuroscience 2009 Abstracts 529.24/J10. Society for Neuroscience, Chicago, IL.

Summary: The relationship between nitric oxide (NO) and cholinergic system in brain has been evidenced by using inhibitors of the nitric oxide synthase (NOS) that blocked cognition, while NO donors can facilitate it. Nevertheless, the participation of NO in the recovery of cholinergic deficit due to the administration of a selective cholinergic immunotoxin, 192 IgG saporin (SAP) has not been studied. The aim in this work was to evaluate the modulation of the nitrergic system after the damage induced by SAP and to measure the response to the administration of a NO donor, molsidomine (MOL). We used adult male Wistar rats allocated into either one of 4 groups: 1) vehicle PBS, 0.1M pH 7.4, 2) intraseptal administration of SAP (0.22 µg), 3) MOL ip 4 mg/kg, 4) SAP+MOL. Striatum, prefrontal cortex and hippocampus were dissected out at different times after treatment and quantification of nitrites, NOS activity and expression were performed. Our results show that SAP induces a reduction on the constitutive NOS activity in prefrontal cortex and striatum (54%, 64% respectively compared with control p<0.05); while hippocampal cNOS tended to decrease. MOL alone improved NOS activity in those regions. Neuronal and endothelial NOS expression (nNOS, eNOS) in the same regions did not change significantly. When the nitrites levels were analyzed, changes were region-specific. We conclude that administration of the NO donor promotes the recovery of cNOS activity in the model of cholinergic denervation associated to 192 IgG SAP. Further cognitive studies are being carried out in order to demonstrate the cholinergic recovery by MOL.

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Thomsen MS, Hay-Schmidt A, Hansen HH, Mikkelsen JD (2009) Poster: Distinct neural pathways mediate alpha7 nicotinic acetylcholine receptor-dependent activation of the forebrain. Neuroscience 2009 Abstracts 646.2/V14. Society for Neuroscience, Chicago, IL.

Summary: α7 nicotinic acetylcholine receptor (nAChR) agonists are novel drugs candidates for the treatment of cognitive deficits in schizophrenia, which have shown pro-cognitive effects in clinical trials. Selective α7 nAChR agonists, such as SSR180711, activate neurons in the medial prefrontal cortex (mPFC) and shell of the nucleus accumbens (ACCshell) in rats, regions which are important for cognitive function. However, the neural substrates involved in these effects remain elusive. Using retrograde tracing from the mPFC with Cholera Toxin B and immunoreactivity of the immediate-early gene c-Fos, a marker of neuronal activation, we identify the horizontal limb of the diagonal band of broca (HDB) in the basal forebrain as an important site of α7 nAChR activation. Approximately 26% of the cortically projecting neurons in the HDB are activated by acute administration of SSR180711 (10 mg/kg), and the neurons activated by SSR180711 in the HDB are cholinergic. Selective depletion of these cholinergic neurons with 192 IgG-Saporin abolishes the SSR180711-induced activation of the mPFC, but not the ACCshell, demonstrating their critical importance for α7 nAChR-dependent activation of the mPFC. Contrarily, selective depletion of dopaminergic neurons in the ventral tegmental area (VTA) with 6-OHDA abolishes the SSR180711-induced activation of the ACCshell, but not the mPFC or HDB. These results indicate that two distinct neural pathways are activated by SSR180711, involving HDB-to-mPFC and VTA-to-ACCshell projections, respectively. The basal forebrain and mPFC are important for attentional function, and may subserve the pro-cognitive effects of α7 nAChR agonists, whereas activation of the ACCshell is implicated in beneficial effects on the positive symptoms of schizophrenia.

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Kline IV RH, Wiley RG (2009) Spinal µ-opiate receptor (MOR)-expressing dorsal horn neurons: Role in modulating pain and opiate analgesia. Neuroscience 2009 Abstracts 560.13/CC72. Society for Neuroscience, Chicago, IL.

Summary: Selective destruction of MOR-expressing interneurons in lamina II of the dorsal horn of the spinal cord increases reflex nocifensive responses to formalin and decreases the anti-nociceptive effects of morphine on the hotplate and in the formalin test. The interpretation of these studies is limited because reflex-based assays may not accurately reflect the cerebral component of nociception. Therefore, we sought to determine the effects of selectively destroying MOR-expressing dorsal horn neurons on baseline operant responses to aversive thermal and mechanical stimuli in a shuttle box task and effects of systemic morphine and naloxone in the same task. The preference apparatus consisted of a 15 X 15 X 30 cm smoked Plexiglas vented chamber placed upon two adjoining temperature-controlled smooth aluminum floor plates (thermal preference task) or one smooth temperature-controlled floor plate adjoined to a room temperature surface covered with 40 grit sandpaper (mechanical preference task). For both preference tasks, response functions were obtained by pairing a 44°C plate or the sandpaper surface with either 11°, 16°, 25°, 38° or 46°C. Rats were intrathecally injected over the lumbar cord with either 625ng of derm-sap (n=7) or blank-sap (n=6) followed by daily thermal or mechanical preference testing on a randomized schedule. Derm-sap treated rats showed enhanced avoidance of aversive thermal stimuli and the aversive mechanical stimulus. Morphine and naloxone significantly altered responses of control rats (blank-sap), but not derm-sap rats, in both thermal and mechanical preference tasks. We interpret these results as showing that the derm-sap lesion produces hyperalgesia/allodynia, impairs the anti-nociceptive and analgesic effects of morphine and therefore indicating that postsynaptic dorsal horn MOR-expressing neurons play a key role in modulating nociception, pain and opiate analgesia. Dysfunction of these neurons may also play a role in pathological pain states.

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Tai S, Leung L (2009) Facilitation of dentate gyrus population spike may involve septohippocampal GABAergic input. Neuroscience 2009 Abstracts 566.18/EE33. Society for Neuroscience, Chicago, IL.

Summary: The medial septum (MS) is known to modulate the neural circuitry in the hippocampus. It have been demonstrated that, in anaesthetized rats, MS stimulation prior to perforant path stimulation facilitated the population spike in the dentate gyrus and such facilitation was unaffected by muscarinic and nicotinic cholinergic antagonists, suggesting that this facilitation may be mediated by septohippocampal GABAergic neurons. To study the effects of septohippocampal neurons in modulating neural circuitry in the dentate gyrus, selective lesion of septohippocampal GABAergic cells was made by infusion of orexin-saporin in the MS. Evoked field potentials were recorded in the dentate gyrus following stimulation of the medial perforant path in urethane-anesthetized rats using multichannel silicon probes and analyzed as current source density. High-frequency stimulation of the pontis oralis (PnO) activated a hippocampal theta rhythm. Theta peak power was attenuated in lesion rats as compared to control (sham lesion) rats. PnO stimulation resulted in a larger average increase in dentate population spike (pSpike) in control rats compared to lesion rats (26.4 ± 8.8 % vs 5.1 ± 8.7 %) but the difference was not significant (P = 0.1082; control n = 9, lesion n = 8). The number of choline acetyltransferase-immunopositive (cholinergic) cells in the MS was not significantly different (P = 0.88, unpaired t-test) between lesion and control rats, while a significant decrease (about 50%) of the number of parvalbumin-immunopositive GABAergic cells in the MS was observed in lesion as compared to control rats (P<0.05, unpaired t-test). The effect of PnO stimulation on the paired-pulse pSpike response versus interpulse interval (30 - 400 ms) was not different between control and lesion rats. No difference between control and lesion rats was detected in the pSpike enhancement after PnO stimulation following scopolamine (5 mg/kg i.p.). Additional studies were needed to demonstrate the facilitation of dentate gyrus population spike by septohippocampal GABAergic neurons.

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Gaykema RP, Thacker GC, Shapiro NJ, Goehler LE (2009) Immunotoxic lesion of hypothalamic noradrenergic/adrenergic input ameliorates the effects of peripheral LPS challenge on sickness behavior and associated brain c-Fos expression. Neuroscience 2009 Abstracts 570.11/EE120. Society for Neuroscience, Chicago, IL.

Summary: Caudal medullary catecholamine neurons that innervate the hypothalamus play a major role in the activation of paraventricular neurons that drive pituitary adrenocorticotropin and adrenal corticosteroid release in response to peripheral pro-inflammatory challenges with interleukin-1 or lipopolysaccharide (LPS). Pro-inflammatory challenges also lead to marked behavioral changes, including fatigue, loss of social interest, anorexia, somnolence, but the precise neuronal mechanisms that underlie sickness behavior remain elusive. We reasoned that the medulla-hypothalamic catecholaminergic pathway may also contribute to the behavioral manifestations in illness. To investigate such possible role, we applied a targeted lesion approach in rats to determine whether or not caudal brainstem catecholaminergic neurons that innervate the hypothalamus are also necessary for the expression of sickness behavior. Anti-dopamine beta hydroxylase antibodies conjugated to saporin (DSAP), when injected into a target region, selectively poisons and destroy noradrenergic/adrenergic neurons that innervate the target. DSAP was micro-injected bilaterally into the hypothalamic paraventricular nucleus (PVN), whereas control rats received unconjugated saporin (SAP controls). Fourteen days later the animals were injected intraperitoneally with either LPS or saline, and 2h later were submitted to the open field to record their exploratory behavior, 1h after which the rats were sacrificed for brain immunohistochemical analyses. LPS-treated SAP control rats showed drastic reduction in exploratory behavior (reduced locomotion distance and velocity). Prior DSAP microinjections largely reversed the LPS-induced reduction in locomotor behavior. The brains of these DSAP rats showed a dramatic loss of noradrenergic innervation of the PVN but also in other parts of the medial, tuberal and tuberomammilary regions of the hypothalamus. The behavioral resilience to LPS coincided with diminished LPS-related c-Fos staining in the PVN, and increased c-Fos staining in the lateral and tuberomammillary regions related to behavior and/or arousal. In summary, our findings support the hypothesis that hypothalamic catecholaminergic projections originating in the lower brainstem play a critical role in the expression of sickness behavior in the context of novelty-induced exploratory activity, but we cannot determine with precision in which part of the hypothalamus the noradrenergic/adrenergic input contributes to the expression of sickness behavior due to extensive collateralization of the ascending projections throughout the hypothalamus.

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Gulino R, Gulisano M (2009) Poster: Expression of cell fate determinants and plastic changes after neurotoxic lesion of adult mice spinal cord by cholera toxin-B saporin. Neuroscience 2009 Abstracts 563.15/DD51. Society for Neuroscience, Chicago, IL.

Summary: Recent studies have attempted to achieve recovery after spinal cord (SC) injury or disease by either increase neurogenesis or stimulate neuroplasticity. Sonic hedgehog (Shh) Notch-1 and Numb are involved in the regulation of stem cell function. Additionally, Notch-1 has a role as modulator of synaptic plasticity. Little is known about the role of these proteins in the adult SC after selective removal of motoneurons. We injected Cholera toxin-B saporin into the gastrocnemius muscle to induce a selective depletion of motoneurons within lumbar mice SC and analysed the expression levels of Shh, Notch-1, Numb, Choline acetyltransferase (ChAT) and Synapsin-I proteins. The functional outcome of the lesion was monitored by grid walk test and rotarod. The neurotoxin lesion determined a motoneuron depletion and a decrease of ChAT and Synapsin-I protein levels in the lumbar SC. ChAT and Synapsin-I appeared correlated each other and with the motor performance, suggesting that the recovery of locomotion could depend from synaptic plasticity. Moreover, we observed a number of proliferating cells within the depleted SC, which were identified as active astrocytes. Shh and Notch-1 appeared reduced in the lesioned tissue and correlated with ChAT and Synapsin-I levels, suggesting a role in modulating synaptic plasticity. Numb expression was also reduced after lesion and appeared correlated with motor performance Therefore, given the role of these proteins in adult neurogenesis, we presume their involvement also in the observed glial reaction. The in vivo manipulation of Shh, Notch-1 and Numb signalling after lesion could be a way to reduce glial reaction and improve functional recovery.

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Huang T-Y, Lin L-S, Chen H-I, Jen C (2009) Chronic treadmill exercise improves cerebellar functions: Alterations in mitochondrial protein expression, rotarod performance, and toxin resistance. Neuroscience 2009 Abstracts 660.18/CC34. Society for Neuroscience, Chicago, IL.

Summary: The effects of exercise on cerebellar functions were studied. Five-week-old male Wistar rats were divided into exercise and sedentary groups. For exercise groups, rats were subjected to 8 weeks of treadmill exercise at moderate intensity. In some groups, rats were administered with OX7-saporin, a cerebellar Purkinje cell toxin, into the lateral ventricle during the 5th week of training. At the end of training period, they were tested for rotarod performance. Brain tissues were obtained for measurement of mitochondria-related protein, including Mfn2, OPA1, Drp1 and CcOx-IV. The morphology of Purkinje cells was also examined by two photon microscopy. Our results showed that exercise training improve rotarod performance, and increased cerebellar protein levels of Mfn2 and OPA1 (mitochondrial fusion proteins) but not Drp1 (mitochondrial fission protein) or CcOx-IV (a mitochondrial complex IV marker). The dendritic field of Purkinje cells was significant modified in exercise groups. OX7-saporin application impaired the rotarod performance and decreased cerebellar Purkinje cell number only in sedentary rats. In summary, chronic exercise enlarged dendritic field of Purkinje cells and improved cerebellar function, including the rotarod performance, the mitochondrial fusion protein expression, and the resistance to toxin insult.

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Jeong D, Hwang Y, Lee D, Chang J (2009) Behavioral and histological characteristics of 192 IgG-saporin injected rats depending on injection site and dose. Neuroscience 2009 Abstracts 526.23/H8. Society for Neuroscience, Chicago, IL.

Summary: Cholinergic neuronal deficits are evident in both Alzheimer’s disease dementia (AD) and vascular dementia (VaD). Forebrain Cholinergic neurons in the nucleus basalis magnocellularis (NBM) project primarily to the neocortex, and those in the medial septum project to the hippocampus and they make an important role in memory function. We used 192 IgG-saporin to mimic deficits of cholinergic neurons at AD and VaD. 192 IgG-saporin is composed with monoclonal antibody had a low affinity to the rat nerve growth factor receptor p75 and ribosomal inactivating protein, called saporin. When injected intracerebroventricularly or directly into the basal forebrain cholinergic complex, 192 IgG-saporin selectively destroys cholinergic neurons. Many experimenters had used 192 IgG-saporin to investigate cholinergic function but it had been used in different doses and sites of lesion. This makes it difficult to compare the degrees of impairment produced by different lesions. Consequently, our aim is observation of behavioral and histological changes depending on injection site and dose of 192 IgG-saporin. We injected 192 IgG-saporin (0.63ug/ul) in medial septum (dose: 0.05ul, 0.1ul, 0.2ul) or lateral ventricle (dose: 6ul, 8ul, 10ul). 192 IgG-saporin injected rats were compared with Dulbecco’s phosphate buffered saline injected rats. Neurological deficit and functional outcome were determined by immuohistochemistry using anti-cholineacetyltransferase antibody and behavioral test, called water maze. In immunohistological study, the extent of the cholinergic lesion was showed in the basal forebrain complex region of 8ul and 10ul of 192 IgG-saporin injected rats. In behavioral study, sham and lesion groups were able to learn the reference aspect of the water maze within 5day of training. In probe test, we observed significant decrease in time in target quadrant, platform and platform crossings, and increase in latency to first crossing at 8ul and 10ul of 192 IgG-sapoin injected rats (p<0.05). Therefore, our study evaluated that 8ul 192 IgG-saporin injections were sufficient to make an AD mimic dementia model.

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