Regulation of the expression of the proenkephalin gene in cultured meningeal fibroblasts: opposite effects of ?1- and ?2-adrenoceptors

Abstract

Meningeal fibroblasts express the proenkephalin gene during embryonal development but terminate the expression shortly before birth. When brought into primary culture at postnatal day 1, the fibroblasts again express the gene. Activation of protein kinase A reduces this expression and thus may contribute to its prenatal termination. Since the noradrenergic innervation of the meninges begins around the time of birth, it was investigated in the present study, how adrenergic agonists affected the levels of proenkephalin mRNA in cultured fibroblasts. The beta 2-adrenoceptor agonists salbutamol and procaterol increased the levels of endogenous cAMP and diminished the concentration of proenkephalin mRNA indicating that the cultured fibroblasts possessed this beta-subtype. In contrast, noradrenaline increased the level of proenkephalin mRNA in a concentration-dependent manner. This effect was independent of endogenous cAMP and was mediated by alpha 1-adrenoceptors. The data indicate that the noradrenergic innervation of the meninges at the time of birth is not responsible for the termination of the proenkephalin gene expression.