Chemical sympathectomy and maternal separation affect neonatal stress responses and adrenal sensitivity to ACTH

Abstract

The participation of sympathetic adrenal innervation in the control of the neonatal adrenocortical system and in changes in adrenal sensitivity after maternal separation for 24 h was tested in 10- and 23-day-old pups. Chemical sympathectomy by guanethidine (20 mg/kg body wt) decreased basal and stimulated corticosterone compound B (B) secretion without affecting adrenocorticotropic hormone (ACTH) release, abolished the enhanced adrenal sensitivity to ACTH induced by maternal separation in 10-day-old pups, but did not modify adrenal sensitivity following ether stress in 23-day-old pups. Guanethidine treatment did not affect body and adrenal weight or adrenal choline acetyltransferase activity, but it increased tyrosine hydroxylase activity at both ages. Both chronic guanethidine treatment and acute corticotropin-releasing factor immunoneutralization reduced plasma B levels after maternal separation without affecting plasma ACTH levels. Maternal separation in 10-day-old pups enhanced basal and stimulated ACTH and B secretion after exposure to ether vapors and insulin-induced hypoglycemia (IIH). In nonseparated pups, IIH did not stimulate ACTH secretion and caused small increases in B secretion; however, the enhanced response of separated pups to IIH was due to the effects of intraperitoneal injection.(ABSTRACT TRUNCATED AT 250 WORDS)