EFFECT OF CONSTANT TEMPERATURES, DARKNESS AND LIGHT ON THE SECRETION OF MELATONIN BY PINEAL EXPLANTS AND RETINAS IN THE GECKO CHRISTINUS-MARMORATUS

The effect of temperature and lighting conditions on the secretion of melatonin by the pineal organ of the nocturnal gecko Christinus marmor atus was studied using in vitro perifusion. In a 12L:12D lighting regi me, a high-amplitude melatonin rhythm was detectable at a constant tem perature of 20 and 30 degrees C but not at 10 or 37 degrees C. There w ere sustained high levels of melatonin in constant darkness and sustai ned low levels in constant light. No retinal melatonin was detected us ing static and perifusion culture techniques. These results show that the pineal organ of C. marmoratus maintains light sensitivity in vitro but does not contain an oscillator coupled to the melatonin synthetic pathway.