Maternal behavior in cyclic and androgenized female rats: role of ovarian hormones.

A comparative study on the induction of maternal behavior (MB) in response to pups was carried out in cyclic and androgenized rats. Moreover, the effects of exposure to ovarian hormones on the induction of MB in response to pups were studied in cyclic and androgenized rats. A high percentage of androgenized and proestrus rats displayed MB after 48 hr of exposure to pups (87.9% and 87.5% respectively). Diestrus day-1 rats were significantly less maternal (37.5%). Ovariectomy did not impair MB in androgenized rats. High serum progesterone levels induced in androgenized rats by treatment with 10 I.U. of HCG (40 hours before pup presentation) or with progesterone silastic implants prevented the onset of MB. Ovariectomy performed 8 hours before HCG administration restored MB. When behavioral testing began 72 hours after HCG treatment, 75% of the rats were maternal 12 hr after exposure to pups. This rapid onset of MB in proestrus and androgenized rats appeared to be estrogen dependent. The presence of progesterone inhibited the maternal response of androgenized rats.