Extracellular H + iontophoresis modifies responses to γ-aminobutyric acid and cyanide of reticulospinal vasomotor neurons in rats

Abstract

Responses of reticulospinal vasomotor neurons, recorded in the rostral ventrolateral reticular nucleus of the medulla oblongata, to γ-aminobutyric acid (GABA) and cyanide microiontophoreses were examined during H + iontophoresis in anesthetized rats. Extracellular H + iontophoresis attenuated GABA-evoked decreases and enhanced cyanide-induced increases in the neuronal activity, but had no effect on the neuronal activity when applied alone. Opposite responses were produced during OH − iontophoresis. Similar effects were also observed on the glycine-evoked inhibition of these neurons during H + and OH − iontophoreses, suggesting that H + modulation of the GABA-evoked inhibition may not result from a specific action at the GABA receptor-channel complex. It is concluded that extracellular H + ions exert a modulatory action on responses of the reticulospinal vasomotor neurons to other neuro-active substances and may significantly contribute to hypoxic-ischemic cardiovascular regulation.