Aβ1～42对不同年龄组大鼠ChAT和AchE活性变化的实验研究

目的 观察大鼠海马注射Aβ1～42后行为学习记忆和ChAT、AchE活性的变化情况。方法 采用Y迷宫测试行为学习记忆情况和比色法测定ChAT、AchE活性变化。结果 成年、老年模型组出现了行为学习记忆障碍,同时基底前脑ChAT活性降低（P〈0．05）,而海马AchE活性变化不明显（P〉0．05）。幼年模型组基底前脑ChAT活性变化不明显（P〉0．05）,但海马区AchE活性降低（P〈0．05）。结论 ChAT活性的变化在Aβ机制中起重要作用,提高ChAT活性是治疗AD的靶点之一。     

Spatial learning in rats: Correlation with cortical choline acetyltransferase and improvement with NGF following NBM damage

Rats display an acquisition deficit in a circular water maze following excitotoxic lesions of the nucleus basalis magnocellularis (NBM). Experiments were therefore performed to determine if acquisition behavior on this task could predict the degree of cortical cholinergic deafferentation and if the acquisition deficit could be pharmacologically reversed. Performance on acquisition was highly correlated with the lesion-induced reduction in cortical choline acetyltransferase (ChAT) activity. Accuracy of spatial behavior was highly correlated to percentage ChAT depletion (r = 0.75). Neither lesioned rats nor controls displayed a retention deficit after a 9-day interval, nor did either group display a passive-avoidance retention deficit. To test the causal relationship between cholinergic dysfunction and spatial behavior, the central nervous system cholinergic enhancer nerve growth factor (NGF) was intraventricularly infused for 4 weeks. NGF infusion resulted in improved acquisition of the water maze task compared to NBM-lesioned rats receiving vehicle infusion and untreated rats with NBM lesions. These studies indicate that the decrease in cortical ChAT activity is likely to be responsible for the observed acquisition deficit and that pharmacological manipulations can be successfully used to improve behavior following NBM lesions.     

Effects of neuromuscular activity on choline acetyltransferase and acetylcholinesterase

Regeneration of the amputated hind limb of the salamander was prevented by the injection of methadone or levorphanol. Blastema failed to develop despite formation of a thick epidermal cap at the wound site. Injection of the narcotic antagonist, levallorphan, blocked blastemal development for 4 wk but normal growth then began. Phalanges appeared 4 wk later than in controls. Naloxone, a potent narcotic antagonist without agonist activity, neither altered blastemal development nor prevented normal regeneration and differentiation. Treatment with the opioids methadone or levorphanol produced some atrophy of the lingual epithelium and taste buds of the salamanders. Neither of the antagonists caused these changes.     

Regional heterogeneity of choline acetyltransferase activity in primate neocortex

Choline acetyltransferase activity in precentral and temporal regions of primate neocortex is 2.5-fold higher than in occipital cortex. These results suggest large differences in the density of innervation in different regions of primate neocortex by the nucleus basalis of Meynert.     

Lack of correlation between cortical levels of choline acetyltransferase and learning scores in rats with globus pallidus lesions

Previous work has shown that rats with lesions of the globus pallidus (GP) exhibit a generalized learning impairment. Data are presented suggesting that this impairment is not due to inadvertent damage to the nucleus basalis magnocellularis. Rats with GP lesions evidenced a significant visual discrimination learning loss and a significant reduction in cortical choline acetyltransferase (ChAT) activity. However, there was no significant correlation between the severity of the learning loss and the amount of reduction of cortical ChAT activity.     

高同型半胱氨酸血症对大鼠学习记忆能力和海马胆碱乙酰基转移酶表达的影响及叶酸的干预作用

目的 探讨高同型半胱氨酸血症(HHcy)对大鼠学习记忆能力和海马胆碱乙酰基转移酶(ChAT)表达的影响及叶酸的干预作用.方法 将30只Wistar大鼠随机分为正常对照组、HHcy组和叶酸干预组,每组10只.在大鼠饮水中添加蛋氨酸[1.0 g/(kg·d)]制作HHcy模型,叶酸干预组大鼠同时给予叶酸[0.4 mg/(kg·d)]灌胃,共持续8周.在实验前后测定各组血浆同型半胱氨酸(Hcy)、叶酸的浓度,给各组大鼠进行Morris水迷宫试验检查学习记忆能力,实验8周后用免疫组化染色观察大鼠海马区ChAT的表达水平.结果 与正常对照组和叶酸干预组比较,HHcy组水迷宫试验的逃避潜伏期明显延长,穿过平台次数明显减少,停留时间明显缩短(P＜0.05～0.01);HHcy组大鼠海马CA3区ChAT阳性细胞平均灰度值明显降低(P＜0.01).叶酸干预组与正常对照组以上各项检查结果 比较,差异无统计学意义.结论 HHcy导致大鼠学习记忆能力下降以及海马CA3区ChAT表达水平降低.补充叶酸能够起到很好的干预作用.     

Axonal transport of choline acetyltransferase and 6-phosphofructokinase activities in genetically diabetic mice

This study examined the anterograde axonal transport of activities of the cytoplasmic enzymes choline acetyltransferase and 6-phosphofructokinase in genetically diabetic C57BL/Ks (db/db) mice and their nondiabetic (+/?) littermates. Diabetic mice exhibited marked reductions in the accumulation of both choline acetyltransferase and 6-phosphofructokinase activity against a constriction of the left sciatic nerve (38% and 51% of nondiabetic values, respectively). Enzyme activities per unit length of unconstricted nerve were not different from those of nondiabetic mice. The nerves of diabetic mice did not accumulate measurable amounts of sorbitol or fructose and showed no myo-inositol depletion. Thus this study concludes that, in diabetic mice, the deficits in anterograde axonal transport of these two enzymes do not arise from the accumulation of sorbitol and fructose nor from depletion of nerve free myo-inositol.     

Choline acetyltransferase and acetylcholinesterase in canine spinal ganglia: increase of choline acetyltransferase activity following sciatic nerve lesion

Activities of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) were measured in the dorsal spinal ganglia, the dorsal spinal root and the spinal cord of the normal adult dogs and following one side transection of the sciatic nerve in the intervals 5, 10, 15 and 21 days respectively. In the spinal ganglia of normal dogs very low ChAT activity was found; it was three orders lower than AChE activity. Within 5-10 days after the nerve section ChAT activity increased almost five times in the spinal ganglia while AChE activity remained without any changes. The elevation of ChAT activity correlated with that in the dorsal roots at 15th day and in the dorsal spinal cord at 21st day after the nerve section. Histochemical "direct-colouring" thiocholine method showed AChE-positive cells were distributed mainly in the peripheral area of the spinal ganglia. The spinal ganglion cells ranged from intensely AChE-positive to AChE-negative without correlation between cell size and AChE activity. The ChAT activity changes were evaluated in correlation to the cholinergic function in the spinal ganglion neurons.     

Increased activity of choline acetyltransferase and acetylcholinesterase in actively epileptic human cerebral cortex

We measured the activities of the cholinergic marker synthetic and catabolic enzymes choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) in surgical specimens obtained from 38 patients immediately following anterior temporal lobectomy for intractable epilepsy. Samples from patients with actively spiking lateral temporal cortex were compared to non-spiking lateral temporal cortex obtained from patients in whom the epileptic discharges were confined to the hippocampus. Mean activities of ChAT and AChE were increased by 25% (P less than 0.01) and 30% (P less than 0.025) respectively in the spiking vs. non-spiking cortex. We suggest that the above-normal activity of these cholinergic marker enzymes may reflect sprouting of cholinergic nerve terminals in spontaneously spiking cortex of some patients and/or increased acetylcholine metabolism secondary to the stimulatory effect of the ongoing epileptic discharge.     

[H]Kainic acid binding and choline acetyltransferase activity in alzheimer''s dementia

The binding of [³H]kainic acid to caudate nucleus membranes prepared from brains of examples of Alzheimer's dimentia and controls has been determined. No changes were detected in either the affinity of the number of kainate binding sites in the Alzheimer samples compared to control, although there was a large decrease in choline acetyltransderase activity.     

Enhancement of choline acetyltransferase activity in coculture of rat septal and hippocampal neurons

We report that choline acetyltransferase (ChAT) activity and neuronal survival were enhanced in rat septal neurons cocultured with hippocampal neurons. The enhancement of ChAT activity also occurred as a result of the addition of hippocampal conditioned medium (HpCM). When septal neurons from embryonic day 17 (E17) rats were cocultured with hippocampal neurons, ChAT activity was increased 2-fold compared with homogeneous culture of septal neurons. By contrast, no increase in ChAT activity was observed in coculture of septal and neocortical neurons. Treatment with HpCM obtained from cultured E19 rat hippocampal neurons enhanced the ChAT activity of E17 rat septal neurons. The enhancement of ChAT activity caused by coculture with hippocampal neurons and that caused by the addition of HpCM were not blocked by the addition of anti-nerve growth factor (NGF) antibody, suggesting that NGF, which is known to increase the ChAT activity of septal neurons both in vivo and in vitro, did not participate in the increase of ChAT activity. These findings indicate that possible target-derived neurotrophic factor(s), other than NGF, from hippocampal neurons enhance(s) the ChAT activity of septal neurons.     

Muscarinic binding and choline acetyltransferase activity in Parkinsonian subjects with reference to dementia

[³H]Quinuclidinylbenzilate ([³H]QNB) binding and choline acetyltransferase (CAT) activity were studied in post-mortem brains from control and Parkinsonian subjects. CAT levels were reduced in the cortex and hippocampus of Parkinsonians. The apparent affinity of [³H]QNB for the muscarinic receptor was higher in both the caudate nucleus and the frontal cortex. Receptor density increased only in the frontal cortex. These changes are discussed in relation to dementia and mental disturbances following anticholinergic treatment frequently observed in Parkinson's disease.     

Differences in choline acetyltransferase but similarities in catecholamine biosynthetic enzymes in brains of two rat strains differing in their response to stress

Rats of the Wistar-Kyoto (WKY) strain are more reactive to stress than Brown-Norway (BN) rats as adjusted by their behavioral and plasma catecholamine (CA) responses to stress. Contrary to the strain differences existing in the periphery, brain CA and their biosynthetic enzyme activities were found to be similar in both strains before and after immobilization stress. However, as in the periphery, choline acetyltransferase (CAT) activity was higher in brains of WKY rats. The results suggest that: (1) pheripheral and central CA systems may be under different genetic control mechanisms, and (2) strain differences in CAT activity may reflect differences in cholinergic systems both in the brain and periphery, which may be important in the behavioral differences observed.     

Regional tyrosine hydroxylase and choline acetyltransferase concentrations in the brains of lymphocytic choriomeningitis-infected mice

The neurotransmitter biosynthesis enzymes tyrosine hydroxylase and choline acetyltransferase were investigated in selected brain areas of Nya : NYLAR mice infected with lymphocytic choriomeningitis (LCM) virus. Statistically significant alterations in the concentrations of both enzymes occurred in the olfactory, caudate, and neocortical regions at 5 days postinfection. No such alterations occurred in mice given cytoxan (150 mg/kg) 3 days postinfection and examined 5 days postinfection. At 10 days postinfection, however, the cytoxan-treated animals had significantly altered enzyme concentrations in the olfactory region, though not in the caudate or neocortex. This alteration appeared to be transitory, since it was not found in cytoxan-treated animals 60 days postinfection. A possible explanation is that virus production or interference in a brain region cycles over a period of hours or days. Still undetermined is whether these neurochemical changes are a primary effect of the virus or a secondary effect due to the immune response. It is noteworthy that cytoxan caused a marked increase in the enzyme activities studied in most of the brain areas.     

Difference in choline acetyltransferase but similarities in catecholamine biosynthetic enzymes in brains of two rat strains differing in their response to stress

Rats of the Wistar-Kyoto (WKY) strain are more reactive to stress than Brown-Norway (BN) rats as adjudged by their behavioral and plasma catecholamine (CA) responses to stress. Contrary to the strain differences existing in the periphery, brain CA and their biosynthetic enzyme activities were found to be similar in both strains before and after immobilization stress. However, as in the periphery, choline acetyltransferase (CAT) activity was higher in brains of WKY rats. The results suggest that: (1) peripheral and central CA systems may be under different genetic control mechanisms, and (2) strain differences in CAT activity may reflect differences in cholinergic systems both in the brain and periphery, which may be important in the behavioral differences observed.     

Nerve growth factor increases choline acetyltransferase activity in developing basal forebrain neurons

Nerve growth factor (NGF) is a neuronotrophic protein. Its effects on developing peripheral sensory and sympathetic neurons have been extensively characterized, but it is not clear whether NGF plays a role during the development of central nervous system neurons. To address this point, we examined the effect of NGF on the activity of neurotransmitter enzymes in several brain regions. Intracerebroventricular injections of highly purified mouse NGF had a marked effect on the activity of choline acetyltransferase (ChAT), a selective marker of cholinergic neurons. NGF elicited prominent increases in ChAT activity in the basal forebrain of neonatal rats, including the septum and a region which contains neurons of the nucleus basalis and substantia innominata. NGF also increased ChAT activity in the hippocampus and neocortex, terminal regions for the fibers of basal forebrain cholinergic neurons. In analogy with the response of developing peripheral neurons, the NGF effect was shown to be selective for basal forebrain cholinergic cells and to be dose-dependent. Furthermore, septal neurons closely resembled sympathetic neurons in the time course of their response to NGF. These observations suggest that endogenous NGF does play a role in the development of basal forebrain cholinergic neurons.     

Alzheimer's disease: choline acetyltransferase activity in brain tissue from clinical and pathological subgroups

Choline acetyltransferase activity was measured postmortem in five brain regions to determine if such activity provided biochemical support for clinical and pathological subgrouping of Alzheimer's disease. Seven patients with Alzheimer's disease were divided into groups based on age at onset, severity of neuropathological changes, history of myoclonus, family history of dementia, cerebellar amyloid plaques, and congophilic angiopathy. Thirty-two age-matched normal control subjects and 17 neurological control patients with Huntington's disease were also studied. Patients with early-onset and late-onset Alzheimer's disease did not differ in the clinical duration of their disease. Choline acetyltransferase activity was significantly lower in patients with early-onset Alzheimer's disease than in age-matched control subjects in frontal cortex, temporal cortex, hippocampus, and cerebellum. In contrast, choline acetyltransferase activity in patients with late-onset Alzheimer's disease was significantly lower than in age-matched control subjects only in hippocampus. There was a tendency for choline acetyltransferase activity to be lower in cortex from patients with early-onset Alzheimer's disease compared with cortex from the late-onset group, and this difference was significant in temporal cortex. Choline acetyltransferase activity was also measured in the substantia innominata from 9 patients with Alzheimer's disease and 5 age-matched control subjects. Subjects with early-onset Alzheimer's disease had significantly lower choline acetyltransferase activity in substantia innominata than did control subjects. Patients with Alzheimer's disease and a history of myoclonus had significantly lower choline acetyltransferase activity than did affected patients without myoclonus. Multivariate regression analysis showed myoclonus to be the single best predictor of low brain choline acetyltransferase activity. These results provide further evidence for clinical, pathological, and biochemical heterogeneity in Alzheimer's disease.