The effects of soft laser (He-Ne) irradiation on pineal parenchyma. Ultrastructural and pinealocyte caryometric modifications.

A study is made of the ultrastructure and variations in pinealocyte caryometric indices in 45 male albino rats (240 +/- 40 gm). Fifteen animals were subjected to exposed pineal body irradiation for 6 continuous minutes with soft He-Ne laser light. The irradiated rats were sacrificed in groups of five 3, 6 and 15 days post-irradiation. The control and sham-operated (craniotomy without irradiation) groups consisted of the same number of animals as the experimental groups. The results show a significant decrease in indices (p less than 0.0005) in all experimental groups in relation to the control and sham-operated animals, although in terms of the latter p for the three days post-irradiation group was 0.002. A progressive and significant decrease (p less than 0.002) was also observed between the experimental groups after 3 and 15 days and after 6 and 15 days, but not between the experimental groups after 3 and 6 days. Ultrastructurally, there were signs of secretory activity increase in the groups after 3 and 6 days, and decrease in such activity after 15 days--along with the appearance of cells of mesoglial lineage. A significant increase was observed in the number of peri-canalicular dark cells. The results are discussed and compared with those of other authors and different light energies.