The intensity of RNA synthesis in cells of the rat brain hemispheres (neurons, astrocytes, oligodendrogliocytes, microgliocytes) was studied by electron microscopic radioautography, and the data obtained were compared with dispersed to condensed chromatin area ratio. The correlation was found between the level of RNA synthesis and dispersed chromatin area. High chromatin dispersity in neuron and intensive NA synthesis in the extranucleolar part of the nucleus made it possible to assume the existence of depression of an especially large genome part and the variability of the proteins produced by this cell.