Quantitative analysis of "synaptic" ribbon profiles in the pineal complex of male and female Pirbright-White guinea pigs.

Previous studies have pointed in the direction of sex differences as well as regional differences in the pineal gland of guinea pigs. In the present investigation these aspects were studied at the electron-microscopic level by quantitating different types of "synaptic" bodies, intrinsic to pinealocytes. The two major types of "synaptic" organelles, ribbons and spherules, did not exhibit regional or sex differences. "Synaptic" structures intermediate in appearance to ribbons and spherules were significantly larger in number in males in the distal region of the pineal gland, compared to females. As previous studies have shown that ribbon and spherule numbers undergo characteristic changes depending on the functional state of the pineal gland, it is concluded that, as far as the "synaptic" organelles are concerned, no clear-cut sex or regional differences appear to exist in the guinea pig pineal gland.