Norepinephrine induces expression of c-fos mRNA through the alpha-adrenoceptor in rat aortic rings

We examined whether norepinephrine at pharmacologically relevant doses induces increased expression of c-fos mRNA in rat aortic rings. c-fos mRNA was expressed at norepinephrine concentrations known to cause minimum and maximum contraction of rat aorta in vitro. At the concentration known to cause maximum contraction, norepinephrine produced a marked and sustained increase of c-fos mRNA expression. Induction of c-fos was blocked completely by the alpha 1-adrenergic antagonist prazosin, partially by the alpha 2-adrenergic antagonist yohimbine, and not at all by the beta-adrenergic antagonist propranolol. A prazosin inhibition curve showed that 1 nmol/L prazosin inhibited 10 micromol/L norepinephrine induced c-fos expression by 40%. At the pharmacologic dose known to cause maximum contraction, norepinephrine induces c-fos mRNA expression through the alpha-adrenoceptor in rat aortic rings.