Selective immunotoxin-induced cholinergic deafferentation alters blood flow distribution in the cerebral cortex

Adult rats received intracerebroventricular (i.c.v.) administration of either phosphate buffer (PBS) or 192 IgG-saporin (Toxin), 3.6 μg rat⁻¹, a cholinergic immunotoxin. Six to eight weeks later, the animals received a continuous intravenous (i.v.) infusion of either physostigmine (4.2 μg kg⁻¹ min⁻¹) or saline, followed by measurement of cerebral cortical blood flow (CBF) with the autoradiographic Iodo-¹⁴C-antipyrine methodology in four groups of animals: Toxin i.c.v.+saline i.v. (n=9), Toxin i.c.v.+physostigmine i.v. (n=6), PBS i.c.v.+saline i.v. (n=6) and PBS i.c.v.+physostigmine i.v. (n=6). Choline acetyltransferase activity (ChAT) was assessed with Fonnum's method in samples of cortical tissue adjacent to the sites of CBF measurement. ChAT decreased in all regions of the Toxin groups when compared to PBS (% decrease: hippocampus=93%, neocortex=80–84%, entorhinal-piriform cortex=42%, amygdala=28%). CBF decreased globally in Toxin+SAL, most severely in posterior parietal and temporal regions (24–40% decrease from PBS+saline). Physostigmine enhanced CBF predominantly in these same areas both in PBS and Toxin animals although to a lesser extent in the latter. Our results demonstrate the importance of cholinergic mechanisms in the control of CBF. The similarity between the topography of CBF decrease following administration of the immunotoxin to that observed in Alzheimer's disease suggests that the CBF pattern observed in this disease may be the result of cholinergic deafferentation.     

Evidence for the presence of antibodies to cholinergic neurons in the serum of patients with Alzheimer's disease

Summary A blind study showing that serum from patients with Alzheimer's disease causes immunolysis of mammalian brain synaptosomes is reported. Control, aged-matched, sera were largely without effect. The immunolysis was directed mainly against cholinergic synaptosomes. The data presented support the hypothesis that autoimmune mechanisms may operate in the pathogenesis of Alzheimer's disease.     

The cholinergic system, EEG and sleep

Acetylcholine is a potent excitatory neurotransmitter, crucial for cognition and the control of alertness and arousal. Vigilance-specific recordings of the electroencephalogram (EEG) potently reflect thalamo-cortical and brainstem-cortical cholinergic activity that drives theta rhythms and task-specific cortical (de-synchronisation. Additionally, cholinergic projections from the basal forebrain act as a relay centre for the brainstem-cortical arousal system, but also directly modulate cortical activity, and thus promote wakefulness or rapid-eye movement (REM) sleep. Disease states such as sleep disorders, dementia and certain types of epilepsy are a further reflection of the potent cholinergic impact on CNS physiology and function, and highlight the relevance and inter-dependence of sleep and EEG. With novel technologies and computational tools now becoming available, advanced mechanistic insights may be gained and new avenues explored for diagnostics and therapeutics.     

The effect of cholinesterase inhibitors on the regional blood flow in patients with Alzheimer's disease and vascular dementia

The effects of therapy with cholinesterase inhibitors (ChE-I) on regional cerebral blood flow (rCBF) disturbances were investigated by means of single photon emission computed tomography (SPECT). The changes in rCBF were compared with the results of the medical examination and neuropsychological tests. The sample consisted of 41 patients with the Alzheimer's dementia (AD) and vascular dementia (VaD). The effect of ChE-I (rivastigmine) treatment was studied on 33 patients, while the nontreated control group consisted of 8 patients. In the treated patients, an increase in the rCBF was observed, while the scores of the neuropsychological tests decreased slightly. In the VaD group, the increase in rCBF was more significant in the frontal regions, whereas in the group with AD in the temporal regions, respectively. In the nontreated patients, a decrease of both rCBF and scores of neuropsychological tests were observed. The scores of the neuropsychological tests correlated with the results of rCBF. Increased levels of acetylcholine in the brain after ChE-I treatment may support the cholinergic regulation of rCBF, and in result increase it. Such effects seem to be more pronounced in the more affected brain regions.     

Behavioural, histological and immunocytochemical consequences following 192 IgG-saporin immunolesions of the basal forebrain cholinergic system

Use of the selective immunotoxin; 192 IgG-saporin, is helping to elucidate the role of the cholinergic system in cognition by overcoming the problems of interpretation associated with the use of non-specific lesioning agents. In separate studies, we have compared the long- and short-term effects of single site and combined saporin lesions of the nucleus basalis magnocellularis and medial septal area, on spatial learning and memory in radial arm and water maze tasks. At 11 months, only rats with combined lesions showed deficits in both radial and water maze tasks, although terminal cholinergic deafferentation was substantial and extensive tissue loss was seen at the injection sites in both single and combined lesions. However, the extensive tissue loss with long-term lesions suggested that behavioural deficits were not solely attributable to cholinergic deafferentation. In contrast, when rats with combined lesions were tested 5 months after lesioning, no deficits were apparent, although there was almost complete loss of choline acetyltransferase- and nerve growth factor receptor-immunoreactivity in the basal forebrain with no tissue damage at the injection sites. This study supports existing literature that selective loss of cholinergic neurons in the basal forebrain does not produce behavioural impairments in standard tasks of learning and memory, but deficits are apparent when damage is non-selective as occurs late after lesioning, confounding interpretation of behavioural data. It further highlights potential problems with this immunotoxin in long-term studies.     

Regional analysis of age-related changes in the cholinergic system of the hippocampal formation and basal forebrain of the rat

In an attempt to clarify conflicting reports of age-related changes in cholinergic systems of the rat hippocampal formation and basal forebrain, we compared aged (40 months) and adult (12 months) male rats using quantitative, regional receptor autoradiography in addition to radiolabelled assays of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE). The activities of ChAT and AChE in Ammon's horn/subiculum are 24% and 38% lower, respectively, in the aged brains. There is also a drop in both ChAT (38%) and AChE (28%) activities in the septum, and a 46% drop in ChAT activity in the nucleus basalis of aged rats. In the septal pole of the hippocampal formation there is no significant change with age in binding of the muscarinic antagonist, tritiated quinuclidinyl benzylate (3H-QNB) in any hippocampal subregion. However, specific binding in the temporal pole is higher in the subiculum (40%), CA (27%), and dentate gyrus (25%) of the aged animals. Because some of the neurons of the diagonal band of Broca project to the temporal areas of the hippocampal formation by way of a ventral pathway, it is possible that with age this septohippocampal pathway is selectively affected. Particularly in Ammon's horn and the subicular regions of the aged rat hippocampus, postsynaptic muscarinic receptors may upregulate to compensate for decreases in presynaptic cholinergic activity.     

The role of basal forebrain in the primary cholinergic vasodilation in rat neocortex produced by systemic administration of cismethrin

The pyrethroid insecticide cismethrin (9 μmol/kg) causes a large blood flow increase in cerebral cortex, without a parallel increase in metabolism. A unilateral lesion of the basal forebrain attenuated the blood flow increase in the cortex ipsilateral to the lesion but augmented that in the contralateral cortex. Cortical choline acetyltransferase was similarly affected. Atropine sulphate substantially reduced the flow increase and was additive to the lesion effects. Systemic cismethrin is thus capable of activating a cholinergic vasodilation in the cortex and, in the parietal cortex at least, a substantial proportion of the flow increase is mediated by extrinsic projections from the basal forebrain.     

胆碱能神经干细胞在阿尔茨海默病小鼠的移植研究

目的 观察胆碱能神经干细胞移植对阿尔茨海默病(AD)小鼠的治疗效果.方法 C57BL/6小鼠基底巨细胞核注射Ibotenic酸制成AD模型.4周后于额叶和顶叶皮质移植小鼠胚胎干细胞源性胆碱能神经干细胞.存移植术后12周,应用HE染色和且日碱乙酰转移酶-绿色荧光蛋白免疫双标染色观察神经干细胞存活和分化情况,以8方向迷宫试验评价小鼠近事记忆的改善程度.结果 胆碱能神经十细胞移植至AD小鼠顶叶和额叶皮质后主要分化为成熟胆碱能神经元,并移行和整合至移植区周围皮质,该区皮质β-淀粉样蛋白表达明显减少,且小鼠的近事记忆明显改善.结论 胆碱能神经十细胞移植可部分重建AD小鼠的胆碱能支配,改善近事记忆损害.     

Estrogen receptor immunoreactivity within subregions of the rat forebrain: neuronal distribution and association with perikarya containing choline acetyltransferase

Administration of the neuroactive steroid hormone estrogen has been shown to effect cholinergic basal forebrain neuronal function. Antibodies directed against the estrogen receptor alpha (ERalpha) revealed dark (type 1) and light (type 2) nuclear positive neurons within the islands of Calleja, endopiriform nucleus, lateral septum, subfields of the cholinergic basal forebrain, bed nucleus of the stria terminalis, striohypothalamic region, medial preoptic region, periventricular, ventromedial, arcuate and tuberal mammillary nuclei of the hypothalamus, reuniens and anterior medial thalamic nuclei, amygdaloid complex, piriform cortex and subfornical organ. In contrast, only a few scattered ERalpha labeled neurons were found in cortex and hippocampus. ERalpha stained cell bodies were not seen in the striatum. Counts of ERalpha labeled neurons in intact female rats revealed significantly more type 2 neurons within the basal forebrain subfields. Quantitation of ERalpha immunoreactive neurons revealed a significant decrease in the relative number of type 1 neurons within the medial septum (MS), horizontal limb of the diagonal band (HDB) and substantia innominata/nucleus basalis (SI/NB) following ovariectomy. Quantitation following choline acetyltransferease (ChAT) immunohistochemistry revealed a significant decrease in the number of ChAT positive neurons within the MS, HDB and SI/NB, but not VDB following ovariectomy. Following ovx, the percentage of double labeled cholinergic basal forebrain neurons also declined significantly within the MS, VDB, HDB and SI/NB. These observations suggest that estrogen effects a subpopulation of cholinergic basal forebrain neurons and may provide insight into the biologic actions of this steroid in Alzheimer's disease.     

去卵巢大鼠胆碱能神经系统改变及雌激素保护作用机制的研究

目的观察去卵巢大鼠胆碱能神经系统的改变及雌激素对其影响。方法利用免疫组织化学染色结合图像分析方法观察去卵巢大鼠海马CA1区胆碱乙酰转移酶(ChAT)的变化;利用RT—PCR方法检测去卵巢大鼠基底前脑神经生长因子(NGF)mRNA表达的变化。结果去卵巢大鼠海马CA1区ChAT的积分光密度(OD)值降低,基底前脑NGFmRNA平均表达水平明显降低,补充雌激素后以上各项指标均明显提高。结论(1)去卵巢大鼠海马CA1区胆碱能神经元ChAT活性下降,基底前脑胆碱能神经元NGFmRNA表达水平降低。(2)雌激素能够上调去卵巢大鼠NGFmRNA表达．而NGF能够增强ChAT的活性。促进乙酰胆碱(Ach)的合成和释放,改善学习记忆能力。     

Postnatal development of cholinergic system in mouse basal forebrain: acetylcholinesterase histochemistry and choline-acetyltransferase immunoreactivity

The distribution of acetylcholinesterase histochemistry and choline-O-acetyltransferase immunohistochemistry in the basal forebrain was studied in newborn mice (P0) and until 60 days of postnatal life (P60). A weak acetylcholinesterase activity was found at P0 and P2 in the anterior and intermediate parts of the basal forebrain, and higher in the posterior region. The intensity of labeling, neuronal size and dendritic growth seems to increase progressively in all regions of basal forebrain from P4 to P10. The AChE+ cell count shows that in the anterior portion of the magnocellular basal nucleus the number of cells does not vary significantly from birth to the second month of postnatal life. However, in the intermediate and posterior portions of the nucleus the mean number of labeled cells increases significantly from birth to the end of the second week of postnatal life (P13). The choline-acetyltransferase immunoreactivity appears only detectable at the end of the first week (P6) as a slight immunoreaction, which increases progressively in intensity at P8, and at P10 seems to attain the same intensity of labeling found at P60. These results seem to indicate that the acetylcholinesterase could have a non-classic cholinergic role in the first stages of postnatal development, acting as a growth and cellular differentiation factor.     

Anti-brain spectrin immunoreactivity in Alzheimer's disease: degradation of spectrin in an animal model of cholinergic degeneration

In a previous work, we described the existence of anti-brain spectrin auto antibodies in Alzheimer's disease (AD) patients (J. Neuroimmunol. 68 (1996) 39–44). In this report, we further support our previous observations, showing that sera from 9 out of 18 AD patients, but none of 14 control subjects, immunoreacted with spectrin synthesized by PC12 cells. In addition, degradation of brain spectrin was found to be greatly enhanced in the frontal cortex of rats subjected to an animal model of cholinergic degeneration. Our data suggest that spectrin degradation and generation of anti-spectrin auto antibodies may be related to the cholinergic degeneration encountered in AD.     

Biochemical pathology and treatment strategies in Alzheimer's disease: Emphasis on the cholinergic system

The neurochemical pathology of Alzheimer's disease (AD) has been consistently shown to involve cholinergic degeneration in the cerebral cortex. This together with evidence from experimental animal studies showing that cholinergic neurones play a role in learning and memory processes has formed the basis of the cholinergic hypothesis of Alzheimer's dementia and the major rationale for neurotransmitter replacement therapy of the disorder.     

Animal models of Alzheimer's disease: experimental cholinergic denervation

Several animal models of AD have been developed, based upon the consistent finding of a presynaptic cholinergic deficit in AD. Significant cell loss in the NBM, the primary cortical cholinergic afferent, has been reported in AD. Lesions of the corresponding nuclei in the rodent and primate produce a persistent cholinergic deficit, but no consistent change in other neurotransmitter systems. Significant mnestic and cerebral metabolic deficits are observed acutely after lesion, which are responsive to pharmacological reversal and recover over time. Administration of AF64A produces similar mnestic and cholinergic deficits as NBM lesion, but these effects may be less responsive to pharmacological reversal. Administration of scopolamine, a muscarinic receptor antagonist, produces transient receptor blockade, mnestic deficits and deficits in cerebral metabolism, which can be reversed with a variety of pharmacological agents. The primary dissociations between these models and the deficits in AD are the lack of pharmacological response and recovery of function in AD patients and the presence of non-cholinergic neurochemical and cytoskeletal abnormalities. Future research should focus upon the systematic production and analysis of non-cholinergic neurotransmitter and cytoskeletal abnormalities to determine the contribution of these factors to the pathology seen in AD and the production of deficit in aged animals, which may more closely approximate the deficits in AD. The analysis of factors involved in recovery of function and pharmacological response in animal models may provide insight into potential treatment approaches to AD.     

The two faces of Alzheimer's disease

Correct classification of patients with dementia is pertinent to proper interpretation of research findings. However, the history of Alzheimer's disease (AD) is characterized by a continuing debate on its nosological status. Cerebrovascular pathology, Lewy bodies, or hippocampal sclerosis in combination with neuropathological signs of AD of only limited severity results in a disease that is essentially different from severe, purely degenerative AD. The clinical signs, course of the disease, and pathological correlates in elderly patients suffering from “mixed dementia of the Alzheimer type,” may differ from those with “purely degenerative Alzheimer's disease” as encountered in relatively young patients. Both clinicians and researchers have much to gain from a perspective that acknowledges the differences between these subgroups of AD patients. It may provide a more realistic perspective, and it holds promise for new opportunities for prevention and treatment. Received: 16 October 1999, Received in revised form: 13 December 1999, Accepted: 12 January 2000     

Depletion of cholinergic neurons in the nucleus of the medial septum and the vertical limb of the diagonal band in dementia with Lewy bodies

The cholinergic basal forebrain is divided into four subregions (Ch1–4), and cholinergic neuronal loss in the nucleus basalis of Meynert (Ch4) has been correlated with cognitive impairments in both Alzheimer’s disease (AD) and dementia with Lewy bodies (DLB). However, the Ch1–2 regions, which provide the major cholinergic innervation to the hippocampus, have not been investigated in DLB. The purpose of this study was to reveal the cholinergic neuronal changes in the medial septum (Ch1) and the nucleus of the vertical limb of the diagonal band (Ch2) of DLB brains. Using choline acetyltransferase (ChAT) immunohistochemistry, we showed that the number of ChAT-immunoreactive neurons in DLB brains was significantly lower than the numbers in AD and non-demented (control) brains. No significant difference in the number of ChAT-immunoreactive neurons was found between the AD and control brains. Moreover, the size of the ChAT-immunoreactive neurons was significantly smaller in the AD and DLB brains than in the control brains. These results show that cholinergic neurons of the Ch1-2 regions are more severely affected in DLB than in AD. Our DLB cases did not fulfill the neuropathologic criteria for definite AD. Furthermore, some Lewy bodies were observed in the Ch1-2 regions. Thus, cholinergic neuronal loss in the Ch1-2 regions might be specific to the pathology of DLB. Taking the distribution of cholinergic fibers in the hippocampus into consideration, this study suggests a possibility that hippocampal cholinergic projection is involved in Lewy-related neurites in the CA2–3 regions, the origin of which remains unclear.     

激肽释放酶-激肽系统及其与急性缺血性脑血管病的关系

激肽释放酶-激肽系统(kallikreinkinin system,KKS)又称激肽系统,广泛存在于动物体内的多个系统,尤其是在心血管系统内分布更为密集.其主要成分为:激肽原(活性因子前体)、激肽释放酶(活性因子前体的激活物,又称为激肽原酶)、激肽(主要活性因子)、激肽酶(活性因子的灭活物).     

The role of clinical neuropsychology in the neurological diagnosis of Alzheimer's disease

Summary This survey on the early diagnosis of Alzheimer's disease (AD) reinstates the role of clinical neuropsychology in describing the cognitive status of AD and its evolution. The role of clinical neuropsychology is restricted to the clinical diagnosis of organic mental deterioration and its contribution to the diagnosis of AD is separate from that of neurology and neuroradiology. The frequency of a single neuropsychological disturbance in early AD patients is illustrated by our own observations.     

Chronic neuroinflammation in rats reproduces components of the neurobiology of Alzheimer''s disease

Inflammatory processes may play a critical role in the pathogenesis of the degenerative changes and cognitive impairments associated with Alzheimer's disease (AD). In the present study, lipopolysaccharide (LPS) from the cell wall of gram-negative bacteria was used to produce chronic, global inflammation within the brain of young rats. Chronic infusion of LPS (0.25 μg/h) into the 4th ventricle for four weeks produced (1) an increase in the number of glial fibrillary acidic protein-positive activated astrocytes and OX-6-positive reactive microglia distributed throughout the brain, with the greatest increase occurring within the temporal lobe, particularly the hippocampus, (2) an induction in interleukin-1β, tumor necrosis factor- and β-amyloid precursor protein mRNA levels within the basal forebrain region and hippocampus, (3) the degeneration of hippocampal CA3 pyramidal neurons, and (4) a significant impairment in spatial memory as determined by decreased spontaneous alternation behavior on a T-maze.