CELLULAR EXPRESSION OF ALPHA-4 SUBUNIT MESSENGER-RNA OF THE NICOTINICACETYLCHOLINE-RECEPTOR IN THE DEVELOPING RAT TELENCEPHALON

By contrast to adult brain, little is known on the development of nico tinic acetylcholine receptor (nAChR) expression. Using a digoxigenin-l abeled riboprobe for in situ hybridization, alpha 4 nAChR subunit mRNA expression was studied in embryonic and postnatal rat neocortex and h ippocampus where it was transiently increased in neuronal subpopulatio ns and preceded cholinergic fiber ingrowth. alpha 4 expression was inc reased in neocortical layer Vlb between E20 and P2 and, about birth, i n dentate gyrus granule cells subsequently decreasing to adult levels. nAChR mRNA expression is increased at the developing neuromuscular en dplate preceding cholinergic innervation which triggers changes in non -a nAChR isoform expression. It has to be elucidated whether similar c hanges may occur in the telencephalon.