Acute dopaminergic blockade by sulpiride stimulates beta-endorphin secretion in pregnant women.

The pars intermedia of the pituitary gland is well developed in most animal species but rudimentary in adult human subjects. Unlike the anterior pituitary, the intermediate lobe metabolizes proopiomelanocorticotrophin (POMC) mainly to beta-endorphin and to alpha-melanotrophin (alpha-MSH). This activity of the pars intermedia is under an inhibitory dopaminergic control. Biochemical and immunohistochemical evidence suggests the hyperplasia of the intermediate lobe during human pregnancy. The present study demonstrates that an acute dopaminergic blockade by sulpiride dramatically increases plasma concentrations of beta-endorphin in pregnant women but not in non-pregnant women providing functional evidence for the intermediate lobe hypothesis.