The effects of hydrogen ion on spinal neurons.

Abstract

The effects of iontophoretically applied hydrogen ion (H+) on neuronal excitability were studied in the spinal cord of cats. The activity of extracellularly recorded neurons of the dorsal horn was either depressed or enhanced by H+ and in most cases of enhancement there was a preceding phase of depression. During intracellular recordings from motoneurons it was found that H+ application usually caused a hyperpolarization accompanied by an increase in cell input resistance. In a smaller number of cells the hyperpolarization was succeeded by a depolarization that was coupled with a decrease in input resistance. In some neurons it was shown that the depolarizing phase was more prominent and had a shorter latency when larger currents were used to eject H+. The varied reports from earlier studies of excitation or inhibition of neuronal excitability by H+ may be in part explainable by our observations that the effects may depend on the concentrations of H+ used.