OXYTOCIN EFFECTS ON LORDOSIS FREQUENCY AND LORDOSIS DURATION FOLLOWING INFUSION INTO THE MEDIAL PRE-OPTIC AREA AND VENTROMEDIAL HYPOTHALAMUS OF FEMALE RATS

When infused into the medial preoptic area of ovariectomized female rats treated with estradiol benzoate (3-mu-g) and progesteron (150-mu-g), oxytocin was found to increase the lordosis frequency and the lordosis duration. Oxytocin administered into the ventromedial hypothalamus increased the lordosis duration but not the lordosis frequency. In the mesencephalic central grey, oxytocin did not significantly affect lordosis. Oxytocin in the ventromedial hypothalamus facilitated lordosis duration at doses which were ineffective in the medial preoptic area. This contrasts with the pattern of results observed for lordosis frequency. These results lend support to the hypothesis that the lordosis-facilitating actions of oxytocin in the ventromedial hypothalamus are due to a permissive effect of progesterone and that the ventromedial hypothalamus and medial pre-optic area may control different aspects of lordosis.