NEUROENDOCRINE SUPPRESSION OF FEMALE COURTSHIP IN A WILD PASSERINE - CORTICOTROPIN-RELEASING FACTOR AND ENDOGENOUS OPIOIDS

During emergencies in their natural environments, vertebrates initiate coping mechanisms that redirect behavior away from nonessential activ ities and towards survival. Reproductive behaviors are suppressed. Evi dence from field studies on passerine birds shows that this inhibition may not depend on the suppression of gonadal sex steroids, since duri ng the breeding season they remain elevated despite activation of the stress response, We hypothesize that an alternate, central mechanism m ediates the inhibition of reproductive behavior during stress in passe rines. In this study, we tested the intracerebroventricular effects of endogenous opioids and corticotropin-releasing factor (CRF), neuropep tides implicated in the stress response, on courtship behavior in wild -caught female white-crowned sparrows. beta-endorphin (beta-EN) signif icantly inhibited copulation solicitation, an estrogen-dependent court ship display, 30 min after treatment. Naloxone, an opioid antagonist, enhanced the behavior. CRF caused a suppression of solicitation that w as reversible by pretreatment with naloxone, suggesting an intermediar y role for endogenous opioids in CRF-induced suppression of courtship. The effects of beta-EN and CRF on solicitation appear to be independe nt of any general effects on locomotor activity. These results support our hypothesis that stress neuropeptides orchestrate coping behaviors in wild birds.