Abstract
α- or β-Adrenergic blockers such as phenoxybenzamine, phentolamine and propranolol were administered subcutaneously or intraperitoneally chronically to intact, adrenal-demedullated (ADMx) and ADMx plus peripherally chemical-sympathectomized rats with intravenous 6-hydroxydopamine. Adrenal and serum corticosterone (B) levels were determined fluorometrically. Basal levels of B were not changed by the chronic administration of the blockers except phentolamine, which elevated significantly the basal levels of B. Diurnal variation of B levels was not changed by the treatment of the blockers. After exposure of the rats to cold stress (4-6℃, 30 min.), serum and adrenal B levels were markedly elevated in all of intact, ADMx and ADMx+peripherally chemical-sympathectomized rats given propranolol in contrast to much smaller elevation with rats given phenoxybenzamine. In the rats given phentolamine, responses of adrenocortical tissue to the stress were slight and not significant. These results will indicate that peripheral α-adrenergic system may be stimulatory and β-adrenergic system may be inhibitory to adrenocortical function via probable changes in ACTH release as the animal was exposed to the stress.
