Males increase progestin receptor binding in brain of female voles

In female prairie voles, behavioral estrus is induced by exposure to an unfamiliar male and ovulation is induced by mating. Experiments were conducted to determine whether a saturable high-affinity progestin binding site (PRC) is present in cytosols of brain tissue from females exposed to male stimuli for a period of time which is sufficient to bring most females into heat. PRC were detected in both the medialbasal hypothalamus (MBH) and preoptic area (POA). However, PRC levels increased in response to male stimuli in the MBH but not in the POA. The lack of an increase in the POA could not be attributed to changes in circulating progesterone. These results indicate that social stimuli can influence cellular events within specific areas of the female brain and suggest that one distinguishing feature between the spontaneous and induced ovulators may be the pattern of estrogen-induced progestin receptors within areas of the brain which are involved with the control of sexual behavior and/or ovulation.