The effects of periodic alteration of the temperature on the rhythmic melatonin release of explanted chicken pineals.

The melatonin rhythm of cultured chicken pineal cells can be synchronized by cyclic environmental effects. Unlike the effects of light on the melatonin secretion, those of the temperature changes are much less known. Similarly, only a few data are available on the interactions between environmental illumination and periodic temperature changes and on the sensitivity of the pineal gland to temperature changes in different ages of animals. We monitored the effects of temperature on chicken pineals for several days in vitro, in a perifusion system under different illumination patterns. The effects of temperature on pineals from chicken of different age were also compared. The phase of the melatonin rhythm was controlled by periodic elevations of temperature under both constant darkness and continuous illumination. These results show that rhythmic changes of temperature prevent desynchronization induced by constant light. Following elevation of the temperature, the melatonin rhythm of pineals of young chickens (less, than 14 weeks old) was altered for 16 - 18 hours. Similar changes in melatonin rhythm were not found in older animals. It is concluded that the sensitivity for temperature changes of the pineal cells is varying with age.