EXPRESSION OF ALPHA-4-1 AND ALPHA-5 NICOTINIC CHOLINOCEPTOR MESSENGER-RNA IN THE AGING RAT CEREBRAL-CORTEX

Although important in neurodegeneration, systematic studies of nicotin ic acetylcholine receptor expression in normal aging human brains are difficult to perform. We have studied the expression of nicotinic rece ptor alpha 4-1 and alpha 5 mRNA in the frontal and parietal isocortex of 3- (young adult), 24- (late middle aged), and 33-month-old (old) ra ts by nonisotopic in situ hybridization. In all groups transcripts wer e mainly present in layer nmr and V pyramidal neurons. The numerical d ensities of alpha 4-1 mRNA-containing neurons with respect to those of cresyl violet-stained neurons decreased with aging in the rat frontal and parietal cortex, while those of alpha 5 mRNA-containing neurons w ere not affected. These findings point to an age-related decrease of t he percentages of numerical densities of alpha 4-1 mRNa-containing neu rons, which has to be taken into account as a possible substrate for t he well-known decrease of nicotine binding sites in the aging cerebral cortex. (C) 1997 Elsevier Science Inc.