Cholinergic mediation of feminine sexual receptivity: demonstration of progesterone independence using a progestin receptor antagonist.
Feminine sexual receptivity can be elicited by the intracerebral administration of muscarinic cholinergic substances in ovariectomized female rats treated with small amounts of estrogen. These experiments were designed to investigate whether this facilitative cholinergic mechanism is dependent upon progesterone. In the first experiment, estrogen-primed animals were injected with RU 38486, a progestin receptor antagonist, 1 h before progesterone or vehicle injection. Injection of RU and progesterone on Day 1 of testing produced animals which were sexually unreceptive. Furthermore, injection of the antagonist without concomitant progesterone produced animals which were unresponsive to progesterone given 24 h later. Thus, RU 38486 itself may be binding to progestin receptors in critical brain regions, preventing progesterone from binding to these same receptors. In Experiment 2, animals made sexually unreceptive by treatment with RU 38486 subsequently became receptive when injected intracerebrally with oxotremorine, a muscarinic agonist. Therefore, activation of progestin receptors does not appear necessary for the cholinergic mediation of sexual receptivity. As in Experiment 1, animals receiving progesterone on Day 1 showed a diminished response to a second progesterone injection 24 h later; an even greater decrease in this response was observed in animals that also received the antagonist on Day 1.
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000502:physiology*; D002799:Cholinergic Fibers / Q000502:physiology; D004963:Estrenes / Q000494:pharmacology; D005260:Female; D015735:Mifepristone; D010095:Oxotremorine / Q000494:pharmacology; D011187:Posture; D011374:Progesterone / Q000502:physiology*; D051381:Rats; D011980:Receptors, Progesterone / Q000502:physiology; D012726:Sexual Behavior, Animal / Q000187:drug effects / Q000502:physiology*
D004963:Estrenes; D011980:Receptors, Progesterone; D015735:Mifepristone; D011374:Progesterone; D010095:Oxotremorine