ONTOGENIC EXPRESSION OF 2 ALPHA-1-ADRENERGIC RECEPTOR SUBTYPES IN THERAT-BRAIN

alpha-1A/D and alpha-1B adrenergic receptor subtype mRNA expression wa s studied during pre- and postnatal rat brain development. Oligonucleo tide probes were generated to distinguish these two homologous subtype s by in situ histochemical analysis in E14, E16, E19, P0, P8, P14, P21 , and adult animals. alpha-1B adrenergic receptor mRNA expression was noted as early as the E14 animal and demonstrated specific regional an d temporal expression. alpha-1A/D adrenergic receptor mRNA expression was limited in the E19 and P0 animal but increased in intensity with a ging. Specific regional and temporal expression differed between the t wo subtypes. The regional localization for both subtypes appeared to b e stable after P21 but the intensity of expression for both subtypes d ecreased between P21 and adulthood, which is a finding that correlates with previous ligand-binding data. Different subtypes of homologous r eceptors have very different ontogenic patterns of distribution and ma y account for previous discrepancies in ligand-binding data and differ ential tissue responses to various ligands during development.