Abstract

Bilateral infusions of glutamate or kainate to the VMH have been shown previously to produce a rapid inhibition of lordosis induced by manual flank stimulation in estrogen (E)-primed female rats. The first experiment of this study examined whether glutamate and its specific receptor agonists AMPA, NMDA, and kainate, produce the same effect on lordosis, other proceptive, receptive, and defensive behaviors and ejaculations by males when administered to the VMH of E and progesterone (P)-primed female rats receiving olfactory, flank and vaginocervical stimulation (VCS) from sexually vigorous males. The obtained results suggest that glutamate specific receptor agonists, but not glutamate, have inhibitory effects on the entire battery of sexual behaviors. The second experiment investigated whether glutamate receptor antagonists AP-5, CNQX and DNQX have a facilitative effect on proceptivity and receptivity in E-, and E and P-primed females. Indeed, glutamate receptor antagonists had a facilitative effect on proceptive and receptive behaviors in both E-, and E and P-primed females, mirroring those of the agonists. Experiment 3 examined the effect of AP-5 on estrus termination induced by VCS with a lubricated glass rod. The hypothesis was that glutamate may be involved in the sexual inhibition observed during estrus termination, therefore administration of a neurochemical that would block its effects should counteract the effects of VCS. Contrary to this hypothesis, AP-5 heightened the behavioral effects of VCS by increasing defensive behaviors and reducing solicitation rates. Altogether, this data set suggests that VMH glutamate receptors play an inhibitory role on female sexual behavior, but that these receptors are not involved in estrus termination.