EFFECT OF HYPOTHALAMIC INFUSION OF A DOPAMINE D-1 RECEPTOR ANTAGONISTON PROLACTIN SECRETION IN THE EWE

In this study we investigated whether dopamine D-1 receptors in the hy pothalamus are involved in the control of prolactin secretion in ovari ectomised, oestradiol implanted ewes. The D-1 antagonist SCH23390 or v ehicle was infused into either the preoptic area (POA) or the ventrome dial hypothalamus (VMH). During infusion into the VMH, prolactin conce ntrations declined significantly and did not return to control values until more than 60 min after the infusions had stopped. In contrast, i nfusion into the POA had no significant effect. These results are in a ccord with the hypothesis that dopaminergic pathways within the hypoth alamus stimulate prolactin secretion via dopamine D-1 receptors in the VMH.