Progestin-facilitated lordosis of hamsters may involve dopamine-like type 1 receptors in the ventral tegmental area

Hamsters are highly-dependent upon the central actions of progesterone (P) to facilitate sexual behavior. P has membrane mechanisms of action in the ventral tegmental area (VTA) to facilitate sexual receptivity of rodents. The present experiments examined whether P's membrane actions in the VTA include dopamine (DA) type 1 (D1) or dopamine type 2 (D2) receptors. Ovariectomized (ovx), estradiol (E2)- and P-primed hamsters were infused with D1 (Experiment 1) or D2 (Experiment 2) antagonists or agonists (0 or 100 ng) to the VTA and tested 30 min later. The D1 agonist, SKF38393, enhanced P-facilitated lordosis. The D1 antagonist, SCH23390, attenuated P-facilitated lordosis. The D2 agonist, quinpirole and the D2 antagonist, sulpiride, had no significant effects on P-facilitated lordosis. These data suggest that, in hamsters, P's actions for lordosis may involve D1 receptors in the VTA.