催产素在大细胞基底核中对大鼠学习记忆的影响

目的：探讨催产素在大细胞基底核（NBM）内对大鼠学习记忆的影响。方法：于Wistar雄性大鼠大细胞基底核内微量注入不同剂量（0,0.2,2,8nmol）的催产素及催产素拮抗剂-阿托西班（Atosiban）,然后用水迷宫检测大鼠的学习记忆能力及其量效关系。结果：NBM内注入2及8nmol催产素组的大鼠找到平台的时间（潜伏期）显著延长,0.2nmol组与对照组比较未见有显著性差异,先注入催产素拮抗剂后再注入催产素,其找到平台的时间与正常组之间没有显著性差异。结论：NBM内的催产素损害了大鼠的学习记忆能力,其作用是通过催产素受体介导的。     

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

The effects of bilateral ibotenic acid-induced lesions of the nucleus basalis magnocellularis (nBM) on the acquisition and retention of several spatial memory tasks were studied in the rat. 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 was also significantly impaired in animals with these lesions. In contrast, the animals with nBM lesions were not impaired in the acquisition of a position habit in a T-maze. In several of the tasks there was evidence of some learning in the lesion animals after substantial training, although they were significantly deficient when compared with the controls. Administration of the cholinergic agonists physostigmine sulfate or pilocarpine nitrate prior to behavioral testing resulted in a rapid and significant improvement in the performance of the lesion animals. The ibotenate-induced lesions significantly reduced the activity of choline acetyltransferase (CAT) in the anterior and the posterior neocortex. Hippocampal CAT activity was not changed. The results indicate that the cholinergic projections originating in the nBM are involved in the learning and memory of spatial tasks.     

Infusion of neurosteroids into the rat nucleus basalis affects paradoxical sleep in accordance with their memory modulating properties.

The neurosteroids pregnenolone sulfate and allopregnanolone affect memory processes in an opposite manner, pregnenolone sulfate acts as a potent memory-enhancer whereas allopregnanolone impairs memory performance. The mechanisms underlying these memory modulating properties have yet to be elucidated. We have previously reported that infusions of either neurosteroid into the nucleus basalis magnocellularis, one of the main forebrain cholinergic nuclei, differentially affect spatial memory in rats. The relationships between memory performance and paradoxical sleep are well documented, therefore we investigated whether neurosteroids infused into the nucleus basalis magnocellularis affected the sleep-wakefulness cycle in rats, measured by electroencephalographic recordings. Results show that pregnenolone sulfate (5 ng) increased by 12%, whereas allopregnanolone (2 ng) decreased by 24%, the duration of paradoxical sleep in the 24 h interval following injection compared to control recordings. Pregnenolone sulfate inhibits GABA(A) receptors whereas allopregnanolone stimulates them. Since cholinergic neurons of the nucleus basalis magnocellularis are GABA-modulated, it may be postulated that these neurosteroids modify paradoxical sleep by acting on the cholinergic transmission. This may account, at least in part, for the memory modulating properties of these compounds.     

Degeneration of hippocampal fibers and spatial memory deficit in the aged rat

Old and young Fisher 344 rats were compared for their ability to learn a delayed alternation task. The old animals displayed significant impairment of alternation learning, and were slower than the young animals. The brains of these animals were examined using a silver degeneration stain, and among old rats there was conspicuous degeneration. The greatest density of degenerating fibers was seen in the hippocampus and in anatomically related tracts, but there was substantial fiber staining in the corpus callosum, anterior commissure, and internal capsule. Examination of the young brains revealed only an occasional fiber. There were no signs of cortical atrophy in the old animals. The histopathology of the aged animals' hippocampus and fiber tracts supports the possibility that the delayed alternation impairment shown by these animals was a result of age related degenerative changes.     

Effect of unilateral decortication on acetylcholine release from the nucleus basalis

Acetylcholine (ACh) is released from the rat nucleus basalis magnocellularis (nbM) following tissue depolarization with 35 mM K+. In the present study, we report that cholinergic neurons within the nbM undergo retrograde changes resulting in a significant reduction in K+-evoked ACh release following cortical lesions.     

Cognitive enhancing properties of thioperamide infused into the nucleus basalis magnocellularis of the rat

Inflammation Research -     

Decreased level of brain acetylcholine and memory disturbance in APPsw mice

To clarify whether amyloid beta protein (Abeta) amyloidosis induces a disturbance of cholinergic system leading to long-term memory deficits, we continuously examined memory disturbance using the passive-avoidance task, and measured Abeta burden and concentrations of acetylcholine in the brain of APPsw transgenic mice. Repetitive retention trials of the passive-avoidance task showed that the long-term memory impairment in APPsw mice appeared from approximately 7.75 months old and progressively advanced. Significant decreases in acetylcholine levels were found in the brains of 10-month-old mice. A few senile plaques appeared in the cerebral cortex and the hippocampus at 8 months old, and increased in size and number with aging. The concentrations of brain Abeta40/42(43) gradually increased from 8 months old and exponentially increased thereafter. Advance of long-term memory disturbance was closely correlated with Abeta40/42(43) burden. These findings suggested that Abeta accumulation induced long-term memory impairment and disturbance of the cholinergic system, and that the passive-avoidance task and measuring acetylcholine were useful methods for evaluating this mouse model as well as Abeta accumulation.     

Kindling of the hippocampus induces spatial memory deficits in the rat

Since kindling produces electrophysiological and morphological changes in the brain area stimulated, it may well affect behavioural functions dependent on the kindled area. Using an 8-arm maze, it was found that hippocampal kindling can induce specific memory deficits in spatial tasks. Reference (long-term) memory as well as working (short-term) memory were impaired. The largest impairment was observed during the period in which generalized convulsions occurred. Working memory but not reference memory impairment was reversible. Hippocampal kindling may be a useful experimental model for investigating behavioural deficits correlated with epileptogenesis.     

Scopolamine induces up-regulation of nicotinic receptors in intact brain but not in nucleus basalis lesioned rats

The effect of chronic scopolamine treatment on muscarinic and nicotinic receptors in frontoparietal cortex in rats was investigated. Administration of the muscarinic antagonist, scopolamine (10 mg/kg i.p./day) for 21 days, produced a significant increase in the density of both muscarinic and nicotinic receptors by 27.7% and 12.1% respectively as measured by the specific binding of (-)-[3H]quinuclidinylbenzilate and (-)-[3H]-nicotine. There was no modification in the affinities for these ligands. Rats, bilaterally lesioned with ibotenic acid at the level of nucleus basalis of Meynert, which innervates the frontoparietal cortex, showed no up-regulation of cortical nicotinic receptors after chronic scopolamine treatment, suggesting the importance of the synaptic integrity in the regulation mechanism.     

Increase of acetylcholine release from cortex of freely moving rats by administration of histamine into the nucleus basalis magnocellularis

Inflammation Research -     

Kynurenic acid protects against the neurochemical and behavioral effects of unilateral quinolinic acid injections into the nucleus basalis of rats

It has recently been demonstrated that kynurenic acid (KYN), an endogenous tryptophan metabolite, provides almost complete protection against the neurotoxic and mnemonic effects of another tryptophan metabolite quinolinic acid (QUIN) on the cell bodies of the nucleus basalis magnocellularis (nbm). The present study further investigated whether unilateral coinjections of KYN and QUIN into the rat nbm antagonized the effects of QUIN alone. Food-deprived rats were pretrained on an eight-arm radial maze, with four arms baited, until choice accuracy stabilized to greater than or equal to 87% correct. Postoperatively, rats were tested on the radial maze for 32 consecutive days. Feeding behavior and locomotor activity were also measured to determine if nonassociative factors accounted for any observed behavioral deficits. QUIN lesions resulted in significantly more working and reference memory errors compared with sham-operated and coinjected animals, which did not differ significantly from each other. There were no reliable group differences in amount of food eaten or locomotor activity. The QUIN group had a reliable decrease in cortical choline acetyltransferase, with no significant changes for the sham and coinjected groups. Results confirm that KYN antagonizes the neurotoxic and mnemonic effects of QUIN alone and suggest that the memory deficits induced by nbm lesions cannot be solely attributed to changes in feeding or locomotor activity.     

Antisense knockdown of the rat alpha7 nicotinic acetylcholine receptor produces spatial memory impairment

Selective and brain penetrating pharmacological antagonists for use in clarifying a role of alpha7 nicotinic acetylcholine receptors (nAChR) in behavioral paradigms are presently unavailable. Studies in alpha7 knock-out mice (KO) have not revealed convincing changes in behavioral phenotype, in particular measures of cognition that include contextual fear conditioning and spatial memory, which may be due to compensatory developmental changes. Therefore, an antisense oligonucleotide (aON) targeted toward the 3'- and 5'-UTR coding regions of the rat alpha7 nicotinic acetylcholine receptor was used. Following central injection of aON into the lateral ventricle of Long Evans rats for 6 days, treated rats exhibited a significant 42% and 25% decrease in alpha7 nAChR densities in hippocampus and cortex, respectively, as measured by [(3)H]-methyllycaconitine (MLA) binding. There was no change in alpha4beta2 densities measured by [(3)H]-cytisine binding. Acquisition of Morris Water Maze (MWM) performance, a measure of spatial memory, was impaired in aON-treated rats. In addition, a reduction in target platform crossings during a subsequent probe-trial was observed. These data demonstrate the ability of this aON to reduce hippocampal and cortical alpha7 nicotinic receptor densities associated with impaired MWM performance and support the specific involvement of the alpha7 nAChR in spatial learning and memory, a phenotype not affected in alpha7 KO mice.     

Serotonin and acetylcholine release response in the rat hippocampus during a spatial memory task.

By using in vivo microdialysis we monitored the extracellular levels of acetylcholine and serotonin in the hippocampus of rats performing a spatial memory task. After rats were trained for 10 consecutive days to master a food-reinforced radial-arm maze task, they were implanted with a microdialysis probe in the dorsal hippocampus. On day 12, rats were tested in the maze and acetylcholine and serotonin outputs were monitored before the test, during the waiting phase and while performing the trials. In trained, food-rewarded rats, hippocampal acetylcholine levels increased during the waiting period (181 +/- 90 of baseline) and further increased during the radial-maze performance to 236 +/- 13% of baseline values, while serotonin levels did not change during the waiting period but increased to 142 +/- 3% during the maze performance. To discriminate whether the increase of acetylcholine and serotonin levels during the testing was associated with memory performance or with food consumption, we monitored hippocampal acetylcholine and serotonin release in rats that were trained, but not food rewarded, or in rats that were not trained, but rewarded only on the test day. In the trained, non-rewarded group, acetylcholine release increased during the waiting phase to 168 +/- 6%, but did not increase further during the task performance. In contrast, no change in serotonin release was observed in this group in any phase of the test. In rats which were not trained, but food rewarded, acetylcholine increased only during the maze period (150 +/- 5%). Serotonin increased gradually and become significant at the end of the trials. (130 +/- 3%). While both neurotransmitters could be implicated in feeding behaviour, only activation of cholinergic neurotransmission appears to be associated with memory function. Our results support the following hypotheses: (i) hippocampal acetylcholine could be involved in attentional and cognitive functions underlying motivational processes; (ii) serotonin could be implicated in non-cognitive processes (i.e. in the control of motor and feeding behaviour). Since serotonin and acetylcholine neurotransmission is simultaneously activated during the spatial memory task, this suggests that these neurotransmitter systems regulate behavioural and cognitive functions.     

Electrophysiological properties of cholinergic and noncholinergic neurons in the ventral pallidal region of the nucleus basalis in rat brain slices

The ventral pallidum is a major source of output for ventral corticobasal ganglia circuits that function in translating motivationally relevant stimuli into adaptive behavioral responses. In this study, whole cell patch-clamp recordings were made from ventral pallidal neurons in brain slices from 6- to 18-day-old rats. Intracellular filling with biocytin was used to correlate the electrophysiological and morphological properties of cholinergic and noncholinergic neurons identified by choline acetyltransferase immunohistochemistry. Most cholinergic neurons had a large whole cell conductance and exhibited marked fast (i.e., anomalous) inward rectification. These cells typically did not fire spontaneously, had a hyperpolarized resting membrane potential, and also exhibited a prominent spike afterhyperpolarization (AHP) and strong spike accommodation. Noncholinergic neurons had a smaller whole cell conductance, and the majority of these cells exhibited marked time-dependent inward rectification that was due to an h-current. This current activated slowly over several hundred milliseconds at potentials more negative than -80 mV. Noncholinergic neurons fired tonically in regular or intermittent patterns, and two-thirds of the cells fired spontaneously. Depolarizing current injection in current clamp did not cause spike accommodation but markedly increased the firing frequency and in some cells also altered the pattern of firing. Spontaneous tetrodotoxin-sensitive GABA(A)-mediated inhibitory postsynaptic currents (IPSCs) were frequently recorded in noncholinergic neurons. These results show that cholinergic pallidal neurons have similar properties to magnocellular cholinergic neurons in other parts of the forebrain, except that they exhibit strong spike accommodation. Noncholinergic ventral pallidal neurons have large h-currents that could have a physiological role in determining the rate or pattern of firing of these cells.     

Kynurenic acid-induced protection of neurochemical and behavioural deficits produced by quinolinic acid injections into the nucleus basalis of rats

Injection of the endogenous tryptophan metabolite, quinolinic acid (120 nmol in 1.0 microliter) unilaterally into the basal forebrain of rats resulted in a significant ipsilateral decrease in cortical choline acetyltransferase activity, suggesting that cholinergic cells of the nucleus basalis magnocellularis (nbm) were damaged. Injected animals also showed a significant deficit in performance on an 8-arm radial maze, compared to sham operated controls, indicating an impairment of memory. Co-injection of another endogenous tryptophan metabolite, kynurenic acid (360 nmol in 1.0 microliter) with quinolinic acid afforded an almost complete protection against the neurotoxic and memory-impairing effects of quinolinic acid alone. These findings support previous reports that kynurenic acid can protect against the neurotoxic effects of quinolinic acid and indicate for the first time that kynurenic acid can also protect against impairments of memory produced by injection of quinolinic acid into the nbm.     

Learning and memory deficits after lesions of the nucleus basalis magnocellularis: reversal by physostigmine

The role of the cholinergic nucleus basalis magnocellularis in spatial learning and memory was studied in the rat. Animals received bilateral injections of ibotenic acid (5 micrograms/microliters) into the region of the nucleus basalis magnocellularis. Six weeks postoperatively they were deprived of food and trained for 5 weeks in a 16-arm radial maze in which 9 of the arms were baited with food. The nucleus basalis magnocellularis-lesioned animals showed significant deficits in the acquisition of the task. Further analysis of the data indicated that this was due primarily to a deficit in reference (long-term) as opposed to working (short-term) memory. After the 5-week training period the nucleus basalis magnocellularis-lesioned animals received intraperitoneal injections of physostigmine sulphate (0.5 mg/kg) 30 min before each daily trial for 1 week. This treatment resulted in a significant improvement in the performance of the spatial memory task on all three measures. The ibotenate lesions reduced the activity of choline acetyltransferase by about 40% in the anterior cortex and by 15% in the posterior cortex. Hippocampal choline acetyltransferase activity was not affected, indicating that the septohippocampal cholinergic projection was spared by the lesions. The activity of glutamate decarboxylase was not affected in any of these regions. These results suggest that the cholinergic projections of the nucleus basalis magnocellularis play an important role in the acquisition of a spatial memory task.     

平行绑定多电极技术研究大鼠基底核毁损对海马自发放电的影响

目的:研究应用平行绑定多电极细胞外记录技术探讨海人藻酸(KA)注射毁损Meynert基底核(NBM)后海马CA1区自发放电活动的改变。方法:雄性SD大鼠在水合氯醛麻醉和脑立体定位仪引导下,KA注射后破坏双侧NBM,一周后用改装的平行绑定多电极记录大鼠海马CA1区自发放电活动。结果:(1)与传统的细胞外单电极或多电极记录相比,本方法电极制备简单、灵活、造价低廉,细胞损伤小,可同时记录单个核团内多个神经元或相邻脑区多个神经元的活动,便于进一步对神经元环路活动进行分析。结合锋电位分类技术,可对单一通道获得的多个神经元活动进行甑别,大大提高实验精度和效率;(2)比较NBM毁损组和对照组核团放电发现:NBM毁损组大鼠CA1区自发放电频率明显减少,其中单个放电与爆发式(burst)放电类型的平均放电频率同时降低;NBM毁损组自发放电类型发生改变,burst数量增加,但burst内发放频率下降,burst间隔延长。结论:(1)平行绑定多电极技术简便、易行、灵活,结合多通道记录技术可为开展神经元环路活动研究提供有力工具;(2)NBM毁损可致大鼠海马CA1区自发放电频率减少和放电模式改变,提示NBM胆碱能系统参与海马环路的神经活动调控,NBM损伤所致海马自发放电活动的改变可能有助于解释阿尔茨海默病认知功能的下降。     

Acetylcholine receptors in dissociated nucleus basalis of Meynert neurons of the rat

Electrical and pharmacological properties of acetylcholine (ACh)-induced currents in neurons dissociated from the nucleus basalis of Meynert (nBM) of immature (2-week-old) rats were investigated with the whole-cell mode of the patch-clamp technique. At a holding potential (V_H) of −50 mV, ACh (10⁻⁴M) evoked a transient inward current mimicked by nicotine (I_nACh), followed by a sustained outward current mimicked by carbamylcholine (I_mACh). The K_D values were 1.2 × 10⁻⁴ M for I_nACh) and 8.7 × 10⁻⁷ M for I_mACh. The reversal potenial of I_mACh was close to E_K. The I_mACh was determined to be elicited via the M₂ muscarinic receptor, based on the differences in sensitivity to muscarinic antagonists such as pirenzepine and AF-DX-116.     

Recovery of cortical acetylcholine output after ganglioside treatment in rats with lesion of the nucleus basalis

The changes in acetylcholine release from the cerebral cortex induced by a unilateral electrolytic lesion of the nucleus basalis and by a treatment with GM1 monosialoganglioside (30 mg/kg i.p. for 20 days) were investigated. Acetylcholine release was measured using the cortical cup technique in rats transected at midpontine level. In the lesioned rats treated with saline an ipsilateral 38% decrease in acetylcholine release was observed. GM1 treatment prevented the decrease and brought about a 30% contralateral increase. These results indicate that GM1 induces a functional recovery of the cholinergic neurons ascending to the cortex.     

Loss of cholinergic neurons in the nucleus basalis induces neocortical electroencephalographic and passive avoidance deficits.

The present experiments were designed to examine the hypothesis that the degeneration of cholinergic nucleus basalis is related to the cognitive and neurophysiological deficits found in old age. Aged (26 months) rats were impaired both in the acquisition of spatial (water-maze) task and retention of passive avoidance task. During aging, neocortical electroencephalographic fast activity was decreased and high-voltage spindles increased. Loss of choline acetyltransferase-positive neurons correlated with the high-voltage spindle incidence and passive avoidance retention deficit. Unilateral ibotenate nucleus basalis lesioning decreased choline acetyltransferase activity in the cortex and produced a large nonspecific subcortical cell loss in young rats. Ibotenate-lesioned rats were impaired in spatial learning and passive avoidance retention in young rats. Quisqualic acid produced a greater decrease in cortical choline acetyltransferase activity and smaller nonspecific subcortical cell loss than ibotenate lesioning. Spatial learning was not impaired, but passive avoidance performance was disrupted. Slow waves and high-voltage spindles were increased and beta activity decreased on the side of either quisqualate or ibotenate nucleus basalis lesioning. These results demonstrate that age-related neurophysiological and cognitive deficits result partially from the loss of cholinergic neurons in the nucleus basalis and that quisqualic acid nucleus basalis-lesioning in young rats may be used as a pharmacological model of the age-related cholinergic neuron loss.