Regional brain distribution and tissue ontogenic expression of a family of alpha-adrenergic receptor mRNAs in the rat.

Probes derived from three unique alpha-adrenergic receptor cDNA clones were used to examine the mRNA distribution of these receptor subtypes in the brain and peripheral tissues through development. The clones for the three subtypes have been isolated from a rat brain cDNA library and are the rat equivalent of the hamster alpha 1B, the rat homolog of the human alpha 2C10 (platelet), and the rat equivalent of the human alpha 2C4 (kidney). Transcripts for all three receptors are present diffusely throughout the adult rat brain, but there are regional variations that are subtype specific. The brain ontogeny of mRNA expression for the alpha 1B and alpha 2C4 subtypes exhibits an almost linear increase from the neonate to the adult, while the alpha 2C10 mRNA transcript remains constant through postnatal day 8 and then declines into adulthood. Peripheral tissues also demonstrate selective expression of these three receptor subtypes. The alpha 1B receptor is expressed in detectable amounts in all tissues examined except adult kidney, while the alpha 2C10 and alpha 2C4 receptors are more selectively localized; the alpha 2C10 receptor RNA is more prevalent in embryonic tissues. Thus, it appears that receptor subtypes of the same family are expressed differentially throughout the brain and peripheral tissues and that this expression is developmentally regulated in an independent manner.