Maternal Behavior Induced in Virgin Rats by Prolactin

Abstract

SummaryIn virgin rats aged 67-81 days, with ovaries stimulated by Prolan or F.S.H. administration during 5 days, the injection of purified and previously heated prolactin induced maternal behavior in 6 of 10 rats after 6-10 injections. Previous conditioning by concaveation was limited to a single 12-hour period in 4 of these rats. The maternal instinct, in somewhat varying degrees, was exhibited by all these rats while the daily subcutaneous injections were in progress. Six of 7 rats of the control and F.S.H. injected groups, all showing little or no maternal behavior during a 25-day test, later developed or greatly accentuated their maternal behavior after 1 to 8 days treatment with prolactin. Four rats which showed no maternal behavior under prolactin also later failed to show such behavior after repriming and 13 days of administration of unfractionated pituitary extract. Prolactin is the anterior pituitary hormone specifically concerned in the activation of maternal behavior in virgin rats.