MELATONIN RECEPTORS IN THE SUPRACHIASMATIC NUCLEI AND PARS TUBERALIS OF TESTOSTERONE INDUCED PHOTORESPONSIVE RATS

The sexual axis of rats can be rendered photoresponsive by testosteron e implants. We have studied in these conditions whether rat pars tuber alis (PT) melatonin receptor density would be decreased after exposure to short photoperiod (SP) like as observed in long day seasonal breed ers. The answer is no, but we observed that testosterone induced a pho toperiod independent decrease in PT melatonin receptor density. These results show that testosterone-induced photosensitivity in rat is not linked to an SP-induced decrease in PT melatonin receptor density. How ever, testosterone regulates PT melatonin receptors independently of t he photoperiod.