The posterior pituitary: regulation of anterior pituitary prolactin secretion.

Removal of the posterior pituitary from anesthetized male rats results in a prompt and significant increase in circulating prolactin that is reversed by the injection of dopamine. Posterior pituitary extracts, which contain high concentrations of endogenous dopamine, inhibit prolactin secretion from isolated anterior pituitary cells. This inhibition is prevented by incubation of the cells with the dopamine receptor antagonist (+)-butaclamol. The data show that posterior pituitary dopamine reaches the anterior pituitary via the short hypophysial portal vessels and participates in the regulation of prolactin secretion.