Effects of naloxone on the acquisition and expression of appetitive and consummatory sexual behavior in male Japanese quail

Previous studies in Japanese quail indicate that central administration of the opioid antagonist naloxone enhances consummatory sexual behavior (CSB). This effect could be related either to a decrease in sexual satiety or to previously documented stimulatory effects of naloxone on GnRH. The present studies were performed to investigate these two possibilities and to explore for the first time opioid involvement in the expression and acquisition of appetitive aspects of sexual behavior (ASB) in castrated, testosterone-treated Japanese quail. Although no effects on either ASB or CSB were observed in response to peripheral naloxone injections, a significant increase in CSB was observed in males receiving central injections of naloxone. Central injections of naloxone had no effect on the acquisition of a social proximity response used to measure ASB. However, compared to controls a greater number of naloxone-treated birds copulated in the test arena on the first day. Overall, these results indicate an inhibitory role for opioids in CSB, and suggest that opioids are differentially involved in different aspects of sexual behavior. (C) 1999 Elsevier Science Inc.