Morphofunctional changes in the pineal gland during dynamic adaptation to hypothermia.

The effects of stress induced by hypothermia (+4 degrees C for 3 h) on the pathways of serotonin metabolism in the pineal gland and on its structure were studied in adult male Wistar rats. These experiments showed that the melatonin-forming function of the epiphysis undergoes phasic changes during adaptation: there was a significant increase during the first 15 min, which was followed by gradual inhibition (to initial by 30 min) and then sharp suppression (at 3 h). Suppression of the functional activity of the pineal gland occurred because of exclusion of a proportion of pinealocytes from the process of active functioning.