Evidence for the involvement of prolactin in the maternal behavior of the hamster.

The hormonal basis of maternal behavior in the hamster has not been clearly established. Treatment of parturient females on the day of delivery with the prolactin release inhibitor, bromocriptine, resulted in a significant disruption of maternal responsiveness at doses as low as 0.5 mg When pregnant females were implanted with ectopic pituitary grafts under the kidney capsule on day 8 or 9 of gestation to elevate circulating prolactin levels, there was no disruption of maternal behavior after bromocriptine injection on the day of delivery. Taken together, these data indicate that prolactin may be an important modulator of the natural onset of maternal behavior at parturition in the hamster.