Potentiation of lactation-induced oxytocin secretion by intracerebroventricular oxytocin in the conscious goat

The release of oxytocin into the cerebrospinal fluid(CSF) and plasma of lactating goats was studied fol-lowing implantation of cisternal and lateral ven-tricular cannulae. Hand milking was associated with a significant increase in plasma concentrations of oxytocin, but no change in plasma concentrations of vasopressin or CSF concentrations of oxytocin. Intra-cerebroventricular (i.c.v.) infusion of oxytocin itself(1 pmol/min for 60 min) had no effect on basal plasma levels of oxytocin. It did, however, markedly poten-tiate the milking-induced increase in plasma oxytocin above the levels achieved during i.c.v. infusion of arti-ficial CSF alone. In the goat, therefore, milking results in a selective release of oxytocin into the plasma, and this release can be potentiated by the presence of increased concentrations of oxytocin in the CSF. J. Endocr. (1988) 116, 273\p=n-\27