Cell activity in monkey caudate nucleus preceding saccadic eye movements

Summary Using a special tetrazolium salt technique, a striking correlation was observed between Na⁺ concentration of the incubation medium and the formation of formazan catalyzed by glutamate dehydrogenase (GDH) in glutaniatergic neuropil areas of the hippocampal formation, cerebellum, and other brain regions. Na⁺ concentrations of 130–150 mmol/l caused maximal formazan production. The GDH catalyzed sodium-dependent increase in formazan production is suggested to be a consequence of the sodium dependence of glutamate uptake in glutaniatergic brain structures supplying the enzyme with substrate.