Electrical stimulation of the medial preoptic area (MPO) interrupted the lordosis reflex, the major receptive component of female rat sexual behavior, without interfering with proceptivity. In contrast, axon-sparing MPO lesions with a neurotoxin enhanced lordosis and diminished solicitatory behavior. The MPO effect on the lordosis reflex was mediated by its projection to the ventral tegmental area (VTA) because electrical stimulation of the VTA had a similar effect. In the urethane-anesthetized rats, electrical stimulation of the VTA elicited antidromic action potentials in neurons in the core of the MPO. In the ovariectomized females and neonatally castrated males, but not in the androgenized females, estrogen increased thresholds and prolonged refractory periods for the antidromic activation. Thus the neural effect of estrogen was limited to those animals that showed lordosis in the presence of this steroid. Estrogen also inhibited neurons in the dorsal part of the MPO, which project to the midbrain locomotor region (MLR), but had an opposite excitatory effect on MLR-projection neurons in the medial part of the lateral preoptic area (mLPO). Estrogen may therefore enhance lordosis by reducing neural impulse flow from the MPO to the VTA. A reduced MPO output to the MLR, combined with an augmentation of the mLPO effect, may culminate in increased locomotion in the female rats in estrus, because the MPO suppresses locomotor activity whereas the mLPO facilitates it.