The appropriate timing of ovulation is controlled not only by signals from the ovary, but also by the circadian clock. By applying the sodium channel blocker, tetrodotoxin, to the hamster SCN we have gained evidence that a sustained output of the circadian clock during the early morning of proestrus may be necessary for activation of the LH surge system. We find that the incorporation of neurons born in adulthood in germinal regions of the hamster brain is regulated both by photoperiod and by testosterone. Furthermore, daylength and testosterone interact to regulate androgen and opiate receptor expression in hamster brain in ways which may explain seasonal changes in sexual behavior and endocrine feedback. Steroidal and photoperiodic regulation of opiate binding in male golden hamsters.
Short days increase sensitivity to methadone inhibition of male copulatory behavior.
Regional distribution of iodomelatonin binding sites within the suprachiasmatic nucleus of the Syrian hamster and the Siberian hamster. Effects of photoperiod and androgen on pituitary function and neuropeptide staining in Siberian hamsters. Control of phase and period of circadian rhythms restored by suprachiasmatic grafts. Effects of photoperiod duration and melatonin signal characteristics on the reproductive systems of male Syrian hamsters . Localization and partial characterization of melatonin receptors in amphioxus, hagfish, lamprey and skate.