POSTNATAL-DEVELOPMENT AND LOCALIZATION OF 5-HT1A RECEPTOR MESSENGER-RNA IN RAT FOREBRAIN AND CEREBELLUM

The localization of the rat brain 5-HT1A receptor mRNA was analyzed by RNAse mapping and in situ hybridization during postnatal development, particularly in the cerebellum. The regional distribution of 5-HT1A m RNA during the first 2 postnatal weeks was different from that found i n adults. In some areas of the immature brain (hippocampus, cerebral c ortex), 5-HT1A mRNA was found in lower density than in the adult brain . In contrast, high concentrations of the transcript were present in o ther brain structures only during the first days after birth. Thus, in the cerebellum, the density of 5-HT1A mRNA decreased markedly from da y 2 to day 9 after birth and could hardly be detected in the adult ani mal. The localization of the mRNA in the molecular/Purkinje cell layer of the immature cerebellum agreed with that of the 5-HT1A receptor pr otein visualized by immmunocytochemistry and was consistent with the h ypothesis that Purkinje cells express this receptor.