Opioid kappa-receptor agonists suppress sexual behaviors in male rough-skinned newts (Taricha granulosa).
Four experiments were performed to evaluate a possible opioid involvement in the regulation of sexual behavior (amplectic clasping of a female) in intact adult male rough-skinned newts (Taricha granulosa) during the breeding season. It was found that an ip injection of bremazocine, a kappa-receptor opiate agonist, can markedly reduce sexual activity and that an ip injection of naloxone can reverse this inhibition in a dose-dependent fashion. In contrast, in male newts that were sexually inactive before treatment, injections of naloxone failed to induce sexual behavior, suggesting that opioid mechanisms do not normally exert a tonic inhibition of amphibian sexual behavior. In addition, an injection of ethylketocyclazocine (another kappa-receptor agonist), but not morphine (a mu-receptor agonist) suppressed sexual behaviors of male newts. These results indicate that opioid mechanisms that include kappa-type opioid receptors may contribute to the regulation of sexual behavior in nonmammalian vertebrates.
Deviche
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Oregon State University, Department of Zoology, Corvallis 97331.
Moore
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FL
D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D001575:Benzomorphans / Q000494:pharmacology*; D003496:Cyclazocine / Q000031:analogs & derivatives* / Q000494:pharmacology; D016314:Ethylketocyclazocine; D008297:Male; D009019:Morphinans / Q000494:pharmacology*; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology*; D011957:Receptors, Opioid / Q000502:physiology; D012455:Salamandridae / Q000502:physiology*; D012726:Sexual Behavior, Animal / Q000187:drug effects*
D000700:Analgesics; D001575:Benzomorphans; D009019:Morphinans; D011957:Receptors, Opioid; D009270:Naloxone; D016314:Ethylketocyclazocine; D009020:Morphine; C027248:bremazocine; D003496:Cyclazocine