[Comparative electron microscopic and autoradiographic study of the "dark" and "light" neurons of the cerebral cortex].

Among the neurons of the frontal pole of the brain cortex in rats in the norm there is a small, increasing with years, amount of "dark" cells, Regularities in their distribution in the cortical layers were not detected. In transition from the optical picture with the use of halfthin sections for the identification of the corresponding cells to an electronomicroscopic study of "dark" neurons it was found that these cells possess a certain type of ultrastructure: an increased number of ribosomes, deep invagination of karyolemms, an expansion of the perinuclear space, a significant number of slit, tortuose channels of the endoplasmatic reticulum, a somewhat increased laminar Golgi complex with large vacuoles. With the aid of autoradiography it was established that there is a drop in the level of the RNA synthesis in the nucleus and a drop in the velocity of the migration of newly formed RNA into the cytoplasma of "dark" cells.