Excitatory effect of amino acids on identified neuron R14 ofAplysia. I. Glycine-induced depolarization and its ionic mechanism

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Abstract
The ionic mechanism of the membrane effect of glycine on identified neuron R14 of Aplysia was investigated with conventional intracellular recording and voltage‐clamp techniques. Both localized and bath applications of glycine markedly depolarize R14. Bath‐applied glycine induced an inward current that gradually reached a maximum and remained at that level until glycine was washed out. Displacement of the holding potential from –46 to –121 mV increased the inward current. The extrapolated reversal potential was +38.6 mV. Reduction of [Na+]o reversibly decreased the inward current. Alterations of [K+]o, [Cl−]o, and [Ca2+]o, as well as bath‐applied ouabain and sodium cyanide, did not affect the inward current. These results suggest that glycine can induce an Na+ current and that the glycine‐induced inward current does not reflect an active uptake by an Na+‐coupled transport system of glycine into the neuron.