Estrogen implants in the medial preoptic area stimulate maternal behavior in male rats

The present study investigated whether the medial preoptic area (MPOA) mediates estrogen stimulation of maternal behavior in the male as it does in the female. Previous studies have shown that lesions of the medial preoptic area prevent sensitization of maternal behavior in male rats and that in gonadectomized, hormonally primed males, systemically administered estradiol benzoate stimulates short-latency maternal behavior. These findings are similar to those found in females. In the present study adult males were gonadectomized and hormonally primed with subcutaneously implanted capsules of estradiol (Days 1-16) and progesterone (Days 3-15) and then were stereotaxically implanted bilaterally in the MPOA with implants containing 10% estradiol. Tests with young pups were started 48 h later and continued for 10 days (11 tests). Control groups were implanted in the MPOA with cholesterol or were injected subcutaneously with estradiol benzoate (100 microg/kg). Estradiol implanted males had shorter latencies for maternal behavior (retrieving, crouching, licking pups) than cholesterol implanted males, but their latencies were slightly longer than those of estradiol benzoate injected males. The medial preoptic area, therefore, mediates estrogen stimulation of maternal behavior in males as it does in females.