Courtship-induced changes in female sexual receptivity : a neuroendocrine study in an amphibian

Graduation date: 1989This thesis describes studies that investigated 1)\ud the effects of courtship on the neuroendocrine system of\ud female rough-skinned newts, Taricha granulosa, and 2)\ud whether the observed courtship-induced neuroendocrine\ud changes affected female sexual receptivity.\ud Sexual behaviors of female T. granulosa changed\ud dramatically during courtship. Initially, females\ud exhibited unreceptive behaviors to a courting male. After\ud several hours of courtship, females displayed receptive\ud behaviors, and males responded by attempting to transfer a\ud sperm cap. Once courtship, insemination and post-insemination\ud behaviors were complete, the female no longer\ud became receptive to future courtship.\ud Both telencephalic irLHRH and plasma estradiol\ud concentrations changed as females became receptive. Early\ud in courtship, when females were unreceptive, irLHRH\ud concentrations in the telencephalon were elevated, but by\ud the time females became receptive irLHRH concentrations\ud were low. The change in telencephalic irLHRH\ud concentration occurred in the nervus terminalis, a little\ud understood cranial nerve that may influence reproduction.\ud Plasma estradiol levels were low at courtship initiation,\ud but were elevated by the time females became receptive.\ud The observations, that irLHRH and estradiol concentrations\ud were associated with changes in female sexual behaviors\ud and that these hormones influence female sexual\ud receptivity in other vertebrates, suggested that courtship\ud by a male activates female sexual behavior by stimulating\ud endogenous changes in LHRH and estradiol.\ud Increasing or decreasing plasma estradiol\ud concentrations or blocking the action of this steroid in\ud the brain were found to have no effect on female\ud receptivity. Also, injecting LHRH or LHRH analogs into\ud brain was found to have no effect on female receptivity.\ud Progesterone implantation inhibited receptivity suggesting\ud that this steroid may be responsible for the post-insemination\ud decrease in female sexual behavior. These\ud results suggest that although courtship induces\ud physiological changes in female T. granulosa, the changes\ud in LHRH and estradiol may not be influencing receptivity