The subnormal choline acetyltransferase (ChoAcTase) activity in the cerebral cortex of patients with Alzheimer disease (AD) is thought to originate from the loss of cholinergic neurons in the nucleus basalis of Meynert (nbM). To examine possible changes in the functional activity of the remainng cholinergic neurons in the nbM of patients with AD, the level of expression of ChoAcTase mRNA was evaluated. A procedure for double-labeulng cholinergic neurons to detect ChoAcTase mRNA and the corresponding protein in the same cell was developed, taking advantage of an anti-ChoAcTase antibody and the recently isolated cDNA complementary to a sequence of the human ChoAcTase mRNA. In the study of three controls and four patients with AD, the presence of both ChoAcTase mRNA and protein was observed in the same large neurons in both nbM and putamen. Specificity of in situ hybridization was further supported by the absence ofneuronal sining with a sense probe. In AD patients a subnormal level of expression of ChoAcTase mRNA per cholinergIc cell was detected in the nbM but not in the putamen. Our data support the hypothesis that expression of ChoAcTase mRNA might be down-regulated in the surviving cholinergic neurons in the nbM of patients with AD, raising the possibility of functional restoration by stimulating ChoAcTase synthesis.In Alzheimer disease (AD) a consistent decrease in choline acetyltransferase (ChoAcTase) enzyme activity has been described in the neocortex, as well as in other cholinergic brain areas (1). The reduction in ChoAcTase activity in the cerebral cortex has been reported to be related to the severity of dementia (2). This decrease is thought to originate from loss or declining function of cholinergic neurons known to be affected in AD. A marked loss of immunolabeled cholinergic neurons has been described in the nucleus basalis of Meynert (nbM) (see ref. 3), as well as in the ventral striatum and pallidum (4,5). However, there is a lack of information regarding the functional state of the remaining neurons. Experimental evidence from animal studies suggests that an absence of specific signals, such as trophic factors, can play a crucial role in cholinergic function and cell survival. One of the best known examples is the action of nerve growth factor (NGF) on cholinergic neurons in nbM and striatum (6)(7)(8).In human postmortem brain tissue, the in situ hybridization is a method by which the state of a neuron at the mRNA level can be examined. We have analyzed the levels ofChoAcTase mRNA, taking advantage of the recently isolated cDNA fragment specific for human ChoAcTase, which allowed synthesis of a complementary RNA probe. Expression of ChoAcTase mRNA was examined by in situ hybridization, coupled with immunocytochemical detection of ChoAcTase protein, in the surviving cholinergic neurons in the nbM and in the putamen of AD patients compared with controls. The results show that (i) the RNA probe was specific for human ChoAcTase mRNA, labeling only neurons that were also stained by the antib...

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The expression of the protooncogene bcl‐2, an inhibitor of apoptosis in various cells, was examined in the adult human brain. Several experimental criteria were used to verify its presence; mRNA was analyzed by northern blot with parallel experiments in mouse tissues, by RNase protection, and by in situ hybridization histochemistry. Bcl‐2 protein was detected by western blot analysis and immunohistochemistry. Two bcl‐2 mRNA species were identified in the human brain. The pattern of distribution of bcl‐2 mRNA at the cellular level showed labeling in neurons but not glia. The in situ hybridization signal was stronger in the pyramidal neurons of the cerebral cortex and in the cholinergic neurons of the nucleus basalis of Meynert than in the Purkinje neurons of the cerebellum. Both melanized and nonmelanized neurons were labeled in the substantia nigra. In the striatum, bcl‐2 mRNA was detected in some but not all neurons. In the regions examined for Bcl‐2 protein, the expression pattern correlated with the mRNA results. In patients with Alzheimer's and Parkinson's diseases, quantification of bcl‐2 mRNA in the nucleus basalis of Meynert and substantia nigra, respectively, showed that the expression was unaltered compared with controls, raising the possibility that the expression of other components of apoptosis is modulated.