HISTOCHEMICAL STUDIES OF SUCCINIC DEHYDROGENASE OF THE BRAIN OF MICE, RATS, GUINEA PIGS AND RABBITS

Succinic dehydrogenase activity of the brain was histochemically investigated in mice, rats, guinea pigs and rabbits. Fresh frozen sections cut at 20 µ were stained with the Seligman-Rutenburg method as modified by Rosa and Velardo. The pattern of enzyme distribution is remarkably similar but the intensity of staining differs somewhat in the animal species, being highest in mice and rats, intermediate in rabbits and lowest in guinea pigs. The enzyme activity is found exclusively in the grey matter and ocurs both in the perikaryon and neuropil. The activity in the grey matter exhibits the characteristic local variations which are ascribed to the varying participation of the nerve cell bodies and surrounding neuropils in the reaction. Nerve cell bodies contain variable amounts of dye particles of different sizes, and the neuropil possesses variable numbers of coarse granules. An intense reaction is given in the caudate nucleus, putamen, anterior nucleus of the thalamus, interpeduncular nucleus and cerebellar cortex. An intermediate activity occurs in the neocortex, rhinencephalon, optic tectum, most of the cranial nerve nuclei, superior and inferior olivary nuclei, and the Goll and Burdach nuclei. A low activity is present in the paraventricular structures, such as supraoptic crest, subfornical and subcommissural bodies, and area postrema, as well as the paraventricular and supraoptic nuclei of the hypothalamus, and dorsal nuclei of the vagus nerve.