In vitro effects of beta-endorphin on testicular release of androgens in the lizard Podarcis sicula Raf.
The effects of the proopiomelanocortin-derived opioid peptide, beta-endorphin (beta-EP), and of the opioid antagonist, naloxone (NAL), on both basal and pituitary-stimulated androgen secretion from superfused quiescent and active testes were assessed in the adult lizard, Podarcis sicula. In the absence of the homologous pituitary, in vitro treatment with beta-EP and/or NAL did not affect basal secretion of androgens from quiescent and active testes. Conversely, in the presence of the homologous pituitary, treatment with beta-EP brought about a decrease in androgen secretion in active testes, but no effect on quiescent ones. Naloxone counteracted the inhibitor effect of beta-EP in active testes, and enhanced maximal pituitary-stimulated secretion of androgens in quiescent but not in active testes. The effects produces by beta-endorphin and naloxone were reversible. These results suggest that, in this lizard, opioids might be involved in the control of androgen release. The lack of effect of beta-EP and naloxone when added directly to the testes seems to suggest that the opioid agonist and antagonist act on androgen release by modulating pituitary gonadotrophin output.
Department of Zoology, University of Naples Federico II, Italy.
G
G
Ciarcia
A
A
Cardone
M
M
Paolucci
V
V
Botte
D000728:Androgens / Q000096:biosynthesis*; D000818:Animals; D066298:In Vitro Techniques; D008116:Lizards; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology*; D009294:Narcotics / Q000494:pharmacology*; D010902:Pituitary Gland / Q000378:metabolism; D013737:Testis / Q000187:drug effects / Q000378:metabolism*; D001615:beta-Endorphin / Q000494:pharmacology*
D000728:Androgens; D009292:Narcotic Antagonists; D009294:Narcotics; D009270:Naloxone; D001615:beta-Endorphin