Sibarov D.A.,Kovalenko R.I., Nozdrachev A.D.
Osmotic Stress Influences The Structure And Function Of The Pineal Gland,
Society for Neuroscience 28th Annual Meet ing, 1998.

Dept. of General Physiology, St.Petersburg State Univ., St.-Petersburg, Russia, 199034.

The pineal gland (PG) has a role in adaptive mechanisms to different conditions of environment. Both pineal connections with the paraventricular and supraoptic nuclei in hypothalamus, oxytocin and vasopressin neuronal terminals in i t’s tissue indicate the involvement of the PG in compensatory reactions during osmotic stress. Melatonin content in blood plasma increases because of hypoxia, hunger, thirst, initial stress attack and carcinogenesis in colon. Experiments were made on Wis tar 48-hour water and food deprived male rats. Electrone microscopy showed the ultrastructural changes mainly in “light” pinealocytes, reflecting increased secretion (numerous secretory vesicles in cell processes, active nuclear chromatin, the secretory matherial in extracellular spaces). Elecrophysiological study of deprived rats demonstrated the growth of frequency of spontaneously active cells discharging, switching of cells from irregular to regular and pattern activity and the appearence of chain-l ike activating groups of cells. The ratio of different cell types shifts to regular and pattern activity types. Action potentials of secretory cells reflects exocytosis. So we suppose “light” cells to be activated mainly. Morphometry of pineal parenchyma mounts in deprived animals revealed increase of vessels volume 1,5-2,5 times, depending of rat individual responsibility to osmotic stress. Total square occupated by “light” cells decreased. Cell lipidization was observed. The “light” cells were olso de monstrated to become smaller. No significant changes in nucleolus sizes were observed. As the result, morphometry data confirmed exocytosis activation revealed by electrone microscopy and in electrophysiological experiments showing smaller sizes of activ e “light” cells because of intensive excretion of secretory product. Capillars expanding in this conditions probably helps hormonal transport to circulating blood.