INVOLVEMENT OF HYPOTHALAMIC SUBSTANCE-P IN THE EFFECT OF PROLACTIN ONDOPAMINE RELEASE

IN order to examine the role of hypothalamic SP in the feedback regula tion of prolactin, we studied the effect of prolactin and dopamine on SP concentration and release, and the effect of SP on dopamine release . Hypothalamic fragments from male Wistar rats were incubated in the p resence of prolactin, dopamine or SP under basal and K+-stimulated con ditions. SP (10(-7) M) stimulated dopamine release, while dopamine (10 (-7) M) decreased SP content and release. Prolactin (100 ng ml(-1)) in creased SP content and release. An increase in hypothalamic SP content was also found during suckling. In addition, a specific antagonist fo r SP, Win 62,577, blocked the effect of prolactin on dopamine release. These results show an interaction between SP and dopamine at the hypo thalamic level and suggest that SP could mediate the feedback action o f prolactin on dopamine release.