Neuron-specific enolase reflects metabolic activity in mesencephalic neurons of the rat

Numerous studies on the local rate of energy metabolism of various brain regions during development and following experimental manipulation have been conducted using 2-deoxyglucose uptake and cytochrome oxidase (CO) histochemistry, both considered to be reliable indicators of long-term and short-term alterations in neuronal activity, respectively. Another method which has been related to neuronal activity is neuron-specific enolase (NSE) immunohistochemistry. An isoenzyme of enolase, a key element in the glycolytic pathway, NSE is present in neurons and neural-related cells e.g. neuroendocrine cells, pituicytes, and many tumor cells, but not in glia. The distribution on adjacent tissue sections of immunoreactive NSE and histochemically determined CO were mapped in the rat mesencephalon and adrenal medulla. Both methods showed highly restricted localization of staining which coincided with few exceptions in the most reactive areas, namely the superior colliculus, medial and lateral geniculate nuclei, red nucleus, lateral mammillary nucleus, interpeduncular nucleus and substantia nigra pars lateralis and pars reticulata. Immunoreactivity of varying intensity for NSE was also observed in perikarya and in processes of numerius scattered neurons throughout the mesencephalon, including the substantia nigra pars compacta, and reticular formation. The general correspondence in staining patterns between CO and NSE in the midbrain, supports the utility of NSE as a useful index of metabolic activity in neurons.