Reduced nicotinamide adenine dinucleotide and depolarization in neurons

Activity of frog dorsal root ganglion neurons, evoked by dorsal root stimulation under aerobic conditions, produced a change in the level of reduced nicotinamide adenine dinucleotide (NADH) on the surface of this tissue. There was a decrease of NADH (oxidation), followed by an increase of NADH (reduction). Both changes were dependent on previous activity, and a critical time is required in order to observe a similar response. At the frequency and duration of stimulation used here, each stimulus evoked neuron depolarization as shown by recording from single cells. The NADH oxidation occurred in the respiratory chain and it was selectively blocked by Amytal. The NAD reduction was attributed to 3-phosphoglyceraldehyde dehydrogenase activity and it was blocked by iodoacetate. The NADH oxidation and NAD reduction were attributed to respiratory chain activity and aerobic glycolysis, both activated and deactivated by changes of phosphate potential (ATP/ADP + Pi). A low phosphate potential activates the respiratory chain and glycolysis; a high phosphate potential deactivates the respiratory chain and glycolysis.