INDUCTION OF PSYCHIC ESTRUS IN THE HAMSTER WITH PROGESTERONE ADMINISTERED VIA THE LATERAL BRAIN VENTRICLE1

Abstract

Baton rouge Following estrone priming, the ovariectomized golden hamster responds to injections of progesterone in adequate doses by exhibiting psychic estrus as do also certain other common laboratory rodents, a fact first established by Frank and Fraps (1945) and subsequently verified by Kent and Liberman (1947) while studying vaginal smears associated with induced mating. While the threshold dose of progesterone necessary to effect psychic estrus when administered via a subcutaneous route has not been established, Frank and Fraps observed no mating among animals subjected to subcutaneous injection of 0.02 mg. of progesterone 24 to 48 hours after estrogen priming, but found that 0.05 mg. of progesterone was as effective in inducing mating as was 10 times this quantity. The purpose of the present paper is to report that doses of progesterone too small to effect psychic estrus when administered subcutaneously to ovariectomized, estrogenprimed females may be entirely adequate in inducing typical mating responses when introduced directly into the ventricles of the brain.