Effects of dexamethasone on phenylethanolamine N-methyltransferase and adrenaline in the brains and superior cervical ganglia of adult and neonatal rats.

Abstract

Abstract— Phenylethanolamine N‐methyltransferase (PNMT) activity assayed by a sensitive radiochemical method was found to be distributed unevenly in the adult rat brain. Highest activities of this enzyme were located in the medulla and the hypothalamus. Small amounts of adrenaline were identified in the hypothalamus using a sensitive enzymatic radiochemical assay procedure, whereas in the medulla and other brain regions the values for adrenaline were at the limits of the sensitivity of the assay for this amine. The daily administration of dexamethasone (1 mg/kg) to adult rats for 13 days significantly increased PNMT activity in medulla and hypothalamus and also increased the adrenaline content of the hypothalamus. Five daily injections of dexamethasone (0·1 mg/kg) to newborn rats did not alter the PNMT activity or the catecholamine content of the brain, but markedly increased the PNMT activity and adrenaline content of superior cervical ganglia. Higher doses of dexamethasone given to newborn rats (6 daily injections of 1 mg/kg) increased PNMT activity both in the medulla and in the hypothalamus.