Pinealocyte subsurface cisterns. II: Influence of time of day, sympathectomy, and castration.

Subsurface cisterns (ssc) of the gerbil pinealocyte were studied by electron microscopic morphometry taking account of different external influences: time of day, sympathetic deafferentation, castration with or without substitution of testosterone. Male individuals of Meriones unguiculatus, aged 150 days, were used. Though ssc number is invariant with respect to the light-dark cycle, ssc size follows a highly significant sinusoid curve. The largest ssc were found in the afternoon, the smallest ones in the early morning. Bilateral resection of the superior cervical ganglia reduces the density of pinealocyte ssc markedly, and their size is maximal or, in relation to the scaled-down cell, unusually large. Castration with or without application of testosterone propionate does not alter pinealocyte ssc, neither with respect to density nor size. From these experimental data it is concluded that pinealocyte ssc may play a supportive role in the regulation of pinealocyte sensitivity, in so far as it depends on receptors located in the cell membrane.