Pars intermedia ACTH and MSH content: effect of adrenalectomy, gonadectomy and a neurotropic (noise) stress.

Pars intermedia (PI) ACTH and melanocyte-stimulating hormone (MSH) content and pars distalis (PD) ACTH concentration were measured following 3 experimentally induced 'perturbations'. The feedback-induced increase in ACTH release following adrenalectomy is not accompanied by a change in PI ACTH and MSH contents, while the feedback-induced increase in gonadotropin secretion following gonadectomy is associated with significant changes in PI ACTH and MSH contents. A well-defined neurotropic (noise) stressor resulted in significant increases in PI ACTH and MSH. A striking finding in all of the studies was a positive correlation between PI ACTH and MSH contents. We conclude that PI ACTH and MSH secretion are altered with feedback-induced alterations in gonadotropin secretion and with neurotropic stressors.