Short-day exposure eliminates the LH response to naloxone in golden hamsters.
Short-day-induced testicular regression in golden hamsters is accompanied by changes in opiatergic control of LH release. Serum LH in long-day-exposed hamsters is elevated by subcutaneous injections of naloxone. By day 42 of short-day exposure, naloxone is unable to stimulate LH secretion; responsiveness to naloxone is restored after reexposure to long days. The change in response to naloxone may reflect a loss of opiate regulation of LH release; an alternative, but not mutually exclusive, hypothesis is that additional opiate-independent mechanisms inhibit LH despite the blockade of opiate LH inhibition by naloxone.
D000818:Animals; D002940:Circadian Rhythm; D006224:Cricetinae; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism*; D008297:Male; D008647:Mesocricetus; D009270:Naloxone / Q000494:pharmacology*; D013737:Testis / Q000502:physiology; D013997:Time Factors
D009270:Naloxone; D007986:Luteinizing Hormone