Differential distributions of oxidative enzymes within subnuclei of the interpeduncular nucleus in rats

Previous research has shown that neuropeptides, biogenic amines, and transmitter-related enzymes are differentially distributed between the subnuclei of the interpeduncular nucleus (IPN). The present study provides evidence that oxidative enzymes also are differentially distributed across IPN subnuclei. Histochemical staining for glucose-6-phosphate dehydrogenase (G6PDH) is most intense in the dorsal-medial subnucleus, followed in order of diminishing intensity by the rostral, rostral-lateral, dorsal-lateral, lateral, central, intermediate, and apical subnuclei. Succinate dehydrogenase (SDH) reaction product is most intense in the central and intermediate subnuclei, followed in order of diminishing intensity by the rostral, rostral-lateral, lateral, dorsal-medial, and apical subnuclei. Since few cell bodies contain reaction product, these enzymes probably are localized predominantly within dendrites and/or axon terminals in the neuropil of the IPN. The present findings suggest that the individual IPN subnuclei have their own distinctive endogenous level of oxidative and general metabolic activity.