Pilocarpine and physostigmine attenuate spatial memory impairments produced by lesions of the nucleus basalis magnocellularis.

Three experiments, with 63 male Long-Evans rats, investigated the effects of bilateral ibotenic acid-induced lesions of the nucleus basalis magnocellularis (NBM) on the acquisition and retention of several spatial memory tasks. Maintenance of spatial memory in a food-search task was impaired following NBM lesions. Acquisition of spontaneous alternation and reinforced alternation in a T-maze, but not the acquisition of a position habit, was also significantly impaired in Ss with these lesions. In several of the tasks, there was evidence of some learning in the lesioned Ss after substantial training, although they were significantly deficient when compared with controls. Intraperitoneal administration of the cholinergic agonists physostigmine sulfate (0.5 mg/kg) or pilocarpine nitrate (3 mg/kg) prior to behavioral testing resulted in a rapid and significant improvement in the performance of the lesioned Ss. Lesions significantly reduced the activity of choline acetyltransferase in the anterior and the posterior neocortex but not the hippocampus. Results indicate that the cholinergic projections originating in the NBM are involved in the learning and memory of spatial tasks. (48 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquisition, retention, and extinction of operant discriminations in rats with nucleus basalis magnocellularis lesions.

Effects of bilateral ibotenic acid lesions of nucleus basalis magnocellularis (NBM) and scopolamine treatment on different aspects of learning and memory in an operant discrimination task were assessed. In Experiment 1, NBM lesions impaired acquisition performance. In Experiment 2, scopolamine lowered response rates but did not affect discrimination accuracy in lesioned or control rats. In Experiment 3, although pretrained rats showed transient increases in commission errors, percentage correct responding remained above chance levels after lesion. During extinction in Experiment 4, operant responding diminished more quickly in pretrained NBM-lesioned rats than in controls, but subsequent reacquisition performance was equivalent in both groups. Results suggest the NBM is importantly involved in discrimination learning, but cholinergic activity may be less critical for memory retention than for acquisition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Muscarinic cholinoceptor subtypes in the rat frontoparietal cortex after ipsilateral lesions of the nucleus basalis magnocellularis

Muscarinic cholinoceptor subtypes (M1 and M2) were studied in membrane particles of the rat frontoparietal cortex 72 h and 1, 2, 3, and 4 weeks after ipsilateral lesioning of the nucleus basalis magnocellularis (NBM). The affinity of the ligand used to characterize muscarinic cholinoceptors, 3H-quinuclidinyl benzilate did not significantly change in lesioned compared with sham-operated rats as well as the density of high affinity (M1) sites. Low affinity muscarinic cholinoceptors (M2 sites) were significantly decreased in NBM-lesioned rats 72 h and 1 week after lesioning. The density of M2 sites did not significantly differ in lesioned rats 2 or 3 weeks after NBM lesioning, but increased, in comparison with sham-operation 4 weeks after NBM lesioning. These findings suggest that frontoparietal M2 muscarinic cholinoceptors, which probably have a presynaptic localization, are sensitive to NBM lesions. Their changes at different times after NBM lesioning suggest the occurrence of loss, compensation and upregulation of cholinergic projections arising to the neocortex from the NBM.     

Administration of phosphatidylcholine increases brain acetylcholine concentration and improves memory in mice with dementia

Studies on the effect of phosphatidylcholine administration on memory are limited. We administered egg phosphatidylcholine to mice with dementia and to normal mice and compared the differences in memory and serum choline concentration, and choline and acetylcholine concentrations and choline acetyltransferase activities of three forebrain regions (cortex, hippocampus and the remaining forebrain). Mice with dementia were produced by mating sibling mice who had impaired memory for > 20 generations. These mice had poor memory and low brain acetylcholine concentration. We administered 100 mg of egg phosphatidylcholine (phosphatidylcholine group) or water (control group) by gavage to each mouse daily for about 45 d. Control mice with dementia had poorer memory in passive avoidance performance and lower brain choline (cortex and hippocampus) and acetylcholine (hippocampus and forebrain excluding cortex and hippocampus) concentrations and lower cortex choline acetyltransferase activity than the control normal mice (P < 0.05). The administration of phosphatidylcholine to mice with dementia improved memory and generally increased brain choline and acetylcholine concentrations to or above the levels of the control normal mice. In normal mice, phosphatidylcholine treatment did not affect memory or acetylcholine concentrations in spite of the great increase in choline concentrations in the three brain regions. Serum choline concentration in mice treated with phosphatidylcholine increased to a similar level in both strains of mice, indicating that the absorption of phosphatidylcholine was not impaired in mice with dementia. The results suggest that administration of egg phosphatidylcholine to mice with dementia increases brain acetylcholine concentration and improves memory.     

Association of sleep parameters and memory in intact old rats and young rats with lesions in the nucleus basalis magnocellularis.

Relations between sleep and memory were examined as a function of aging in rats. Sleep (24 hr), passive avoidance retention, and choline acetyltransferase (CAT) activity were assessed in 3 age-groups (6, 15, and 24 months old). Age-related alterations were evident in sleep, memory, and cortical and striatal CAT activity. Retention deficits in old rats were significantly correlated with several measures of paradoxical sleep. Similar analyses in 6- and 15-month-old rats with ibotenic acid-induced lesions of the nucleus basalis magnocellularis (NBM) showed several alterations in sleep, memory, and cortical CAT activity comparable to those seen in the old rats. One measure of paradoxical sleep, bout duration, correlated significantly with retention scores in rats with lesions. Thus, fragmented paradoxical sleep accompanies memory impairments in old rats and in young rats with NBM lesions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Organizational changes in cholinergic activity and enhanced visuospatial memory as a function of choline administered prenatally or postnatally or both.

This experiment was an examination of the effects of supplemental dietary choline chloride given prenatally (to the diet of pregnant rats) and postnatally (intubed directly into the stomachs of rat pups) on memory function and neurochemical measures of brain cholinergic activity of male albino rats when they became adults. The data demonstrate that perinatal choline supplementation causes (a) long-term facilitative effects on working and reference memory components of a 12-arm radial maze task, and (b) alternations of muscarinic receptor density as indexed by [–3H]quinuclidinyl benzilate (QNB) binding and choline acetyltransferase (ChAT) levels in the hippocampus and frontal cortex of adult rats. An analysis of the relationship between these organizational changes in brain and memory function indicated that the ChAT-to-QNB ratio in the hippocampus is highly correlated with working memory errors, and this ratio in the frontal cortex is highly correlated with reference memory errors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lesions of rat perirhinal cortex exacerbate the memory deficit observed following damage to the fimbria-fornix.

Rats that had received bilateral lesions of the perirhinal cortex, fimbria-fornix, combined lesions of both these structures, or sham operations were tested on an object-guided delayed non-match-to-sample task. Perirhinal lesioned and fimbria-fornix lesioned rats were moderately impaired when delay intervals of 30 s or more were introduced between the sample and test phases of the experiment. Animals with combined lesions displayed a considerably greater impairment than animals with lesions of either structure alone. The combined lesioned animals were severely impaired in the initial acquisition of the task and displayed a profound memory deficit at delay intervals of greater than 4 s. These results emphasize the importance of the perirhinal cortex to memory function and suggest that the perirhinal cortex and the hippocampal formation may function interactively in the execution of memory processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nerve gas-induced seizures: role of acetylcholine in the rapid induction of Fos and glial fibrillary acidic protein in piriform cortex

Soman (pinacolymethylphosphonofluoridate), a highly potent irreversible inhibitor of acetylcholinesterase (AChE), causes seizures and rapidly increases Fos and glial fibrillary acidic protein (GFAP) staining in piriform cortex (PC). This suggests that the inhibition of AChE by soman leads to increased acetylcholine (ACh) and neuronal excitability in PC. The sole source of cholinergic input to PC is from the nucleus of the diagonal band (NDB). To investigate the role of ACh in soman-induced seizures, we lesioned cholinergic neurons in NDB unilaterally with 192-IgG-saporin. By 10 d, saporin eliminated staining for choline acetyltransferase (ChAT), the synthetic enzyme for ACh, in NDB ipsilateral to the lesion. Staining for AChE, the degradative enzyme for ACh, was eliminated in PC ipsilateral to the lesioned NDB. By 45-60 min after soman, increased Fos and GFAP staining in PC was evident only ipsilateral to the unlesioned NDB. By 90-120 min after soman, Fos and GFAP staining increased bilaterally in PC. In a second experiment, electrical stimulation electrodes were implanted unilaterally in the NDB to activate focally the projections to PC in unanesthetized rats. Within 5 min of NDB stimulation, there were clear behavioral and EEG signs of convulsions. After 45-60 min of NDB stimulation, there was increased Fos and GFAP staining in layer II of PC ipsilateral to the stimulation site. Pretreatment with the selective muscarinic receptor antagonist scopolamine blocked the convulsions and prevented increased Fos and GFAP staining in PC. These results suggest that ACh release in PC triggers the initiation of seizures and gliosis after soman administration, predominantly by the activation of muscarinic receptors.     

Effects of lesions of the nucleus basalis magnocellularis on the acquisition of cocaine self-administration in rats

The nucleus basalis magnocellularis (NBM) is one element in the limbic cortical-ventral striatal circuitry that has been implicated in reinforcement processes. The present study examined the involvement of the cholinergic neurons of the NBM in mediating aspects of cocaine reinforcement. Lesions of the NBM were made by injecting 0.01 M AMPA into the subpallidal basal forebrain. Following 4 days' recovery, rats were implanted chronically with catheters in the jugular vein. In three separate experiments, rats were trained to acquire cocaine self-administration under a FR1 schedule of reinforcement at doses of 0.25, 0.083 and 0.028 mg/injection. A dose-effect function was also determined at the end of the acquisition experiments using five different doses of cocaine (0.009, 0.028, 0.083, 0.25, 0.50 mg/injection) and saline which were presented once daily in a Latin square design. There were no significant differences between groups in the acquisition of cocaine self-administration at any of the three doses studied (0.028, 0.083 and 0.25 mg/injection), although at the lowest dose, lesioned animals responded at greater levels on both active and inactive levers. However, a shift to the left in the cocaine dose-response function was observed revealing that the lesioned group self-administered significantly higher amounts of low doses of cocaine than control rats. These data suggest that the integrity of the NBM is not a critical determinant of the reinforcing effects of cocaine during the acquisition of self-administration of the drug, but that NBM-dependent cholinergic mechanisms may nevertheless interact with the neural substrates mediating the reinforcing properties of cocaine. The data are relevant to recent hypotheses of functional interactions between the dopaminergic system and the cholinergic NBM.     

The neurosteroid pregnenolone sulfate increases cortical acetylcholine release: a microdialysis study in freely moving rats

The effects of pregnenolone sulfate (Preg-S) administrations (0, 12, 48, 96, and 192 nmol intracerebroventricularly) on acetylcholine (ACh) release in the frontal cortex and dorsal striatum were investigated by on-line microdialysis in freely moving rats. Following Preg-S administration, extracellular ACh levels in the frontal cortex increased in a dose-dependent manner, whereas no change was observed in the striatum. The highest doses (96 and 192 nmol) induced a threefold increase above control values of ACh release, the intermediate dose of 48 nmol led to a twofold increase, whereas after the dose of 12 nmol, the levels of ACh were not different from those observed after vehicle injection. The increase in cortical ACh reached a maximum 30 min after administration for all the active doses. Taken together, these results suggest that Preg-S interacts with the cortical cholinergic system, which may account, at least in part, for the promnesic and/or antiamnesic properties of this neurosteroid.     

Cortical cholinergic impairment and behavioral deficits produced by kainic acid lesions of rat magnocellular basal forebrain.

The rat magnocellular basal forebrain (MNBF) is homologous to the human nucleus basalis of Meynert, a structure implicated in the cholinergic hypothesis of cognitive impairment in Alzheimer's disease (AD). In the present study, 18 male Sprague-Dawley rats with kainic acid lesions in the MNBF were compared with 6 unoperated controls, 10 sham-operated controls, and 6 controls injected with kainic acid in the cortical area directly above the MNBF. MNBF lesions depleted choline acetyltransferase in cortex but not in striatum or hippocampus. Cortical dopamine levels were unchanged; serotonin levels were unchanged in hippocampus and parietal cortex but decreased in frontal cortex. Compared with controls, MNBF-lesioned Ss were impaired in 24-hr retention, but not acquisition, of a passive avoidance task with escapable footshock. The groups did not differ in mean number of daily avoidances on a barpress active avoidance task, although learning was slower in MNBF-lesioned Ss. In a serial spatial discrimination reversal test, MNBF-lesioned Ss performed significantly worse than controls. This model may be useful for studying the role of the cholinergic system in memory and possibly for developing treatment strategies to alleviate the cognitive dysfunction of AD. (63 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Choline is a selective agonist of alpha7 nicotinic acetylcholine receptors in the rat brain neurons

In the present study, we demonstrate that choline, a precursor of acetylcholine (ACh) and a product of acetylcholine hydrolysis by acetylcholinesterase (AChE), acts as an efficient and relatively selective agonist of alpha7-containing nicotinic acetylcholine receptors (nAChR) in neurons cultured from the rat hippocampus, olfactory bulb and thalamus as well as in PC12 cells. Choline was able to activate postsynaptic and presynaptic alpha7 nAChRs, with the latter action resulting in the release of other neurotransmitters. Although choline was approximately one order of magnitude less potent than ACh (EC50 of 1.6 mM for choline and 0.13 mM for ACh), it acted as a full agonist at alpha7 nAChRs. In contrast, choline did not activate alpha4beta2 agonist-bearing nAChRs on hippocampal neurons, and acted as a partial agonist at alpha3beta4-containing nAChRs on PC12 cells. The ethyl alcohol moiety of choline is required for the selective action on alpha7 nAChR. Exposure of cultured hippocampal neurons for 10 min to choline (10-100 microM) resulted in desensitization of the native alpha7 nAChRs. Moreover, chronic exposure (10 days) of the cultured hippocampal neurons to a desensitizing concentration of choline (approximately 30 microM) decreased their responsiveness to ACh. The selective action of choline on native alpha7 nAChRs suggests that this naturally occurring compound may act in vivo as an endogenous ligand for these receptors. Putative physiological actions of choline include retrograde messenger activity during the development of the mammalian central nervous system and during periods of elevated synaptic activity that leads to long-term potentiation.     

New clinical issues in celiac disease

The present study examined, in rats with N-methyl-D-aspartate-induced lesions of the basolateral amygdala, the effects of long-term adrenalectomy (i.e. 12-13 weeks) on memory for spatial and cued learning in a water maze. In sham amygdala-lesioned rats, adrenalectomy induced impairments in acquisition and retention performance for the spatial, but not the cued water-maze task. The adrenalectomized rats sustained selective degeneration and death of granule cells in the dentate gyrus dorsal blade. Continuous supplementation of the animals' drinking water with an extremely low dose of corticosterone (20 microg/ml) did not block the retention deficit, but blocked the acquisition deficit and the dentate gyrus neurodegenerative changes. The finding that the memory impairments and dentate gyrus neurodegeneration are dissociable supports the view that the adrenalectomy-induced memory effects are due to the loss of activational effects of circulating adrenal hormones at the time of learning. In adrenalectomized rats which received corticosterone as well as those which did not, lesions of the basolateral amygdala blocked the impairing effects of adrenalectomy on spatial learning and memory. However, the basolateral amygdala lesions did not affect the neurodegenerative changes in the dentate gyrus. In conclusion, the present findings provide further evidence that the basolateral amygdala is involved in regulating stress hormone effects on learning and memory.     

Parallel recovery of MK-801-induced spatial learning impairment and neuronal injury in male mice

The relationship between spatial learning impairment and reversible neuronal injury in the posterior cingulate/retrosplenial (PC/RS) cortex induced by MK-801 in male mice was studied using a four-corner holeboard task. Mice were dosed with 1 mg/kg MK-801 and tested on acquisition of a new "baited" hole at 5 or 12 h posttreatment. Acquisition in drugged mice was impaired at 5 h, but not at 12 h posttreatment. Their retention performances were unaffected 24 h after either the 5 or 12 h posttreatment acquisition sessions. MK-801 (1 mg/kg) was found to induce locomotor hyperactivity and some sensorimotor impairment at 5 h posttreatment. which could have contributed to the acquisition deficit. However, nonassociative effects of the drug were not prominent because this same dose did not impair holeboard performance at 5 h posttreatment when the task was well learned. Histologic experiments showed that many injured neurons (containing cytoplasmic vacuoles) were present in the PC/RS cortex at 5 h posttreatment but the reaction was essentially reversed at 12 h posttreatment. The results suggest that the acquisition impairment and neuronal injury induced by MK-801 evolve and recover in parallel according to a similar time schedule.     

Effects of metrifonate on impairment of learning and dysfunction of cholinergic neuronal system in basal forebrain-lesioned rats

Several studies have indicated the possibility of using cholinesterase (ChE) inhibitors as therapeutic drugs for Alzheimer's disease. Metrifonate (MTF) is an organophosphorus compound that has been used in the treatment of schistosomiasis. In this study, we investigated the effects of MTF on the impairment of learning and memory, decreased ChE activity and extracellular acetylcholine (ACh) levels in basal forebrain (BF)-lesioned rats. The oral administration of MTF improved the BF-lesion-induced impairment of performance on passive avoidance task. Further, MTF reduced ChE activity in the cerebral cortex. In vivo brain microdialysis studies showed that MTF significantly increased the release of ACh, but decreased that of choline (Ch) in the cerebral cortex of BF-lesioned rats. These results indicated that MTF ameliorates the impairment of performance on passive avoidance task in BF-lesioned rats by increasing the extracellular ACh levels by inhibiting ChE. This suggested that MTF may be useful as a therapeutic drug for Alzheimer's disease.     

Involvement of entorhinal cortex or parietal cortex in long-term spatial discrimination memory in rats: Retrograde amnesia.

Twenty-four rats assigned to 1 of 3 matched groups (control, entorhinal cortex [EC], and parietal cortex [PC]) were trained on 6 successive discrimination problems (2 in an 8-arm for pretraining and 4 in a 12-arm radial maze for training per se). The training on the 12-arm maze started 6, 4, 2 and 0.5 weeks before surgery. On the day after the rats learned the last problem, they were given surgery according to groups. Postoperative retention was measured by presenting 16 trials per session for each of the problems during 4 sessions. Results indicate that the EC lesions produced a retention deficit for problems learned immediately and up to 4 weeks before surgery, but not for the problem acquired 6 weeks before the lesions. The PC lesions produced a significant retrograde amnesia that was not temporally graded. Results demonstrate that the EC and PC make important, albeit distinct, contributions to spatial memory storage and retrieval in rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acetylcholine contents and muscarinic receptor levels in frontal cortex, corpus striatum, and hippocampus of reserpinized rats and mice

The acetylcholine (ACh) levels in rat and mouse frontal cortex increased 155% and 124%, respectively, 24 h after ip reserpine 3 mg.kg-1. Striatal ACh contents, however, were diminished by 47% in rats and 80% in mice. ACh contents elevated 50% and scopolamine (Scop) depleted the ACh by 47% in mouse striatum 12 h following reserpine. Receptor binding assay showed that 24 h after reserpine the Bmax of [3H]quinuclidinyl benzilate ([3H]QNB) binding to muscarinic receptors increased in frontal cortex (by 33% in rats, by 30% in mice) and decreased in striatum (31% in rats, 26% in mice). In mouse hippocampus the ACh contents, Bmax, and affinity of muscarinic receptors lowered 63%, 19%, and 26%, respectively. But these changes were not seen in rat hippocampus.     

Microencapsulated nerve growth factor: effects on the forebrain neurons following devascularizing cortical lesions

In this study, we report the effects of nerve growth factor (NGF) delivered into the CNS via a novel delivery system for prolonged, controlled release. The effectiveness of NGF incorporated in the biodegradable microspheres was investigated in the rat model for central cholinergic degeneration. Mature male rats were unilaterally lesioned by disruption of the pia arachnoid vessels and vehicle (alginate microspheres without NGF) and microencapsulated NGF was placed at the site of the lesion. Choline acetyltransferase (ChAT) activity was measured in the nucleus basalis magnocellularis (NBM) and cortex in the (a) non-lesioned control animals; (b) lesioned animals treated with 'empty' microspheres and (c) lesioned animals treated with microspheres containing NGF, 30 days following surgery. Similarly lesioned animals received NGF via permanently installed cannulae in order to compare the novel route of administration with the more conventional one. Immunocytochemical results showed an absence of the cholinergic cell body shrinkage in the NBM otherwise observed in lesioned animals. Furthermore, an increase in intensity of ChAT immunostaining in NGF-treated, lesioned animals was evident. The present results stress the experimental therapeutic possibilities of novel delivery systems for administration of trophic factors in the CNS.     

Acetylcholine release from the frontal cortex during exploratory activity

The activation of the cortical cholinergic system was investigated in 3- and 25-month-old male Wistar rats, by measuring by transversal microdialysis the changes in cortical extracellular acetylcholine (ACh) levels during the performance of simple spontaneous tasks involving exploratory activity and working memory. Two days after implantation of the microdialysis probe in the frontal cortex, object recognition was investigated by either moving the rats from the home cage to the arena containing the objects or keeping the rats in the arena and introducing the objects. Spontaneous alternation was investigated in a Y runway. Young rats discriminated between familiar and novel objects and alternated in the Y runway, while aged rats were unable to discriminate. Whenever rats were moved from the home cage to the arena, ACh release increased (+70-80%) during the exploratory activity. Handling per se had no effect on extracellular ACh levels. When young rats were left in the arena, introduction of the objects caused some exploratory activity and object recognition but no increase in ACh release. ACh release increased by about 300% during spontaneous alternation. In aging rats basal extracellular ACh levels and their increase after placement in the arena were less than half that in young rats. Our work demonstrates that a novel environment activates the cortical cholinergic system, which presumably is associated with arousal mechanisms and selective attentional functions. It also demonstrates that in aging rats the cortical cholinergic hypofunction is associated with a loss of non-spatial working memory.     

Demonstration of membrane estrogen binding proteins in rat brain by ligand blotting using a 17beta-estradiol-[125I]bovine serum albumin conjugate

Trasina is a herbal formulation of some Indian medicinal plants classified in Ayurveda, the classic Indian system of medicine, as Medhyarasayanas or drugs reputed to improve memory and intellect. Earlier experimental and clinical investigations have indicated that the formulation has a memory-facilitating action. In this investigation, the effect of Trasina, after subchronic administration for 21 days, was assessed on two rodent models simulating some biochemical features known to be associated with Alzheimer's disease (AD). The models, in rats, included intracerebroventricularly (i.c.v.) administered colchicine (15 micrograms/rat) and lesioning of nucleus basalis magnocellularis (nbm) by ibotenic acid (10 micrograms/rat). Retention of an active avoidance response was used as the memory parameter. In addition, the effect of Trasina was evaluated on i.c.v. colchicine-induced depletion of acetylcholine (ACh) concentrations, reduction in choline acetyltransferase (ChAT) activity, and decrease in muscarinic cholinergic receptor (MCR) binding in rat brain frontal cortex and hippocampus. The behavioral and biochemical investigations were done 7, 14, and 21 days after colchicine or ibotenic acid lesioning. Trasina (200 and 500 mg/kg) was administered orally (p.o.) once daily for 21 days, the first drug administration being given just prior to lesioning. Colchicine and ibotenic acid induced marked retention deficit of active avoidance learning that was attenuated in a dose-dependent manner by Trasina after 14 and 21 days of treatment. Frontal cortical and hippocampal ACh concentrations, ChAT activity and MCR binding was significantly reduced after colchicine treatment. Trasina (200 and 500 mg/kg) reversed these deficits after 14 and 21 days of treatment. The findings indicate that the herbal formulation exerts a significant nootropic effect after subchronic treatment that may be due to reversal of perturbed cholinergic function.