Corticotrophin-Releasing Hormone Stimulates Neurohypophyslal Hormone Release through an Interaction with the Intermediate Lobe of the Pituitary.

Abstract Corticotrophin-releasing hormone is found co-localized with oxytocin in the magnocellular-neurohypophysical system but its function in this context is unknown. We tested its effects on neurohypophysical hormone secretion in vitro, in the presence and absence of the intermediate lobe of the pituitary. Corticotrophin-releasing hormone caused significant, calcium-dependent secretion of oxytocin and vasopressin from neural lobes in contact with intermediate lobes, i.e. neurointermediate lobes. This effect was inhibited by the dopamine agonist, bromocriptine. Corticotrophin-releasing hormone had no effect on isolated neural lobes in the absence of the intermediate lobe, but alpha- and gamma-melanocyte-stimulating hormone produced an increase in secretion that was comparable in pattern and magnitude to the effect of corticotrophin-releasing hormone on neurointermediate lobes. These findings suggest that corticotrophin-releasing hormone released with oxytocin may act in a paracrine fashion to stimulate release of intermediate peptides which, in turn, can directly evoke release of oxytocin and vasopressin from neural lobe terminals.