Short Latency Induction of Estrous Behavior with Intracerebral Gonadal Hormones in Ovariectomized Rats

Abstract

In an attempt to localize the site of action of progesterone in facilitating sexual receptivity, ovariectomized rats were primed sc with 2 μg estradiol benzoate (EB) for 3 days, and on the fourth day progesterone crystals were applied directly to the brain by inserting a hormone-containing tube into chronic cannulae implanted unilaterally in the lateral and medial preoptic area (MPOA), anterior hypothalamus, ventromedial-arcuate area, or the caudal mesencephalic reticular formation (MRF). Also, in similarly primed animals bearing chronic cannulae in the MPOA or the MRF, EB was applied directly to the brain. Lordosis behavior was quantified 15, 30, 60, 90 and 120 min after progesterone application and compared to pretest values. Progesterone in the MRF significantly increased lordosis behavior in 15 min, while in the other regions progesterone had no effect even after 2 hr. To test the specificity of this response an empty tube, tubes containing cholesterol, procaine, or serotonin were similarly implanted ...