In the ventral tegmental area, progestins have actions at D1 receptors for lordosis of hamsters and rats that involve GABAA receptors

In the ventral tegmental area (VTA), progestins facilitate lordosis via actions at γ-aminobutyric acid (GABA)A/benzodiazepine receptor complexes (GBRs) and dopamine type 1 receptors (D1). The relationship between progestins' actions at GBRs and D1 in the VTA for facilitating sexual behavior of hamsters and rats was examined. Ovariectomized (ovx), estradiol (E2; 10 μg) + progesterone (P; 250 μg; SC)-primed hamsters, with bilateral guide cannulae to the VTA, were pre-tested for sexual and motor behavior and infused with the GBR antagonist bicuculline (100 ng/side) or vehicle. Thirty minutes later, hamsters were re-tested and then infused with the D1 agonist SKF38393 (100 ng/side) or vehicle. Hamsters were post-tested 30 min later. Ovx, E2 (10 μg)-primed rats were pre-tested, infused first with bicuculline or vehicle, second with SKF38393 or vehicle, third with 5α-pregnan-3α-ol-20-one (3α,5α-THP; 0, 100, or 200 ng) and were post-tested 10 and 60 min after 3α,5α-THP infusions. VTA infusions of SKF38393 increased lordosis of hamsters or rats. Bicuculline pretreatment reduced SKF38393- and/or progesterone-mediated increases in lordosis of E2-primed hamsters. In E2-primed rats, bicuculline blocked SKF38393- and/or 3α,5α-THP-mediated increases in lordosis. There were no effects on motor behavior. Thus, in the VTA, GBR activity modulates D1-mediated actions for lordosis of hamsters and rats.