AGING-RELATED SUBUNIT EXPRESSION CHANGES OF THE GABA(A) RECEPTOR IN THE RAT HIPPOCAMPUS

Aging-related changes in the subunit expression of some hippocampal GA BA(A) receptors have been found. Quantitative in situ hybridization ha s revealed that alpha(1) subunit messenger RNA expression was signific antly increased in the hippocampus (34%) of old rats. The largest incr eases were observed in the dentate gyrus (76%) and in the CA1 field (3 0%). Quantitative immunocytochemistry also showed increased protein ex pression of the alpha(1) subunit in the dentate gyrus (19%) and CA1 (1 4%) of old rats. The increased alpha(1) messenger RNA and protein expr ession led to increased proportions of assembled GABA(A) receptors tha t contained alpha(1) subunits, as revealed by quantitative immunopreci pitation of (H-3)flunitrazepam and (H-3)muscimol binding. In contrast, there were no significant changes in the expression of beta(2), beta( 3) and total gamma(2) (gamma(2S) + gamma(2L)) subunits, although a sli ghtly increased expression of gamma(2L) peptide was detected in the hi ppocampus proper (7%), but not in the dentate gyrus. The results are c onsistent with the notion that in the rat hippocampus there is an agin g-related change in the subunit composition of some GABA(A) receptors. Copyright 1996 IBRO. Published by Elsevier Science Ltd.