Selective enrichment of cholinergic neurons with the alpha-ketoglutarate dehydrogenase complex in rat brain

Numerous reports suggest a close interaction between acetylcholine homeostasis and oxidative metabolism. However, the neuroanatomical basis of this relationship has not been established. A previous study showed that a key mitochondrial enzyme, alpha-ketoglutarate dehydrogenase complex (KGDHC) occurs at low levels in neurons, glia and neuropil throughout the rat brain. Some regions including those that are enriched with a cholinergic neuronal marker, choline acetyltransferase (ChAT) show relatively high perikaryal enrichment of KGDHC. The current study utilized double label immunofluorescence to determine whether cholinergic neurons are enriched with KGDHC in rat brain. In cranial nerve nuclei, trapezoid nucleus, nucleus ambiguous and inferior olive, virtually all cholinergic neurons were enriched with KGDHC. However, in basal forebrain nuclei, only a subpopulation of cholinergic cells were intensely immunoreactive for KGDHC. These data provide morphological evidence to support the hypothesized link between cholinergic function and oxidative metabolism in specific brain regions.