Proton-Gated Ion Currents in Neurons of the Rat Spinal Ganglia and the Action of Ketanov on These Currents

Abstract

We studied the desensitization kinetics of currents activated in neurons of the rat dorsal root ganglia (DRG) by short-term shifts of extracellular рН to 6.0 under conditions of primary culture using a whole-cell patch-clamp technique and intracellular perfusion. Changes of these currents under the action of ketanov were also examined. According to the decay parameters, all the observed proton-gated currents could be divided into three groups, with monoexponential fast, monoexponential slow, and biexponential desensitization kinetics. Neurons with fast monoexponential decay were divided, in turn, into two subgroups. In neurons of subgroup 1А, the decay time constant τ varied from 160 to 250 msec (n = 32), while in subgroup 1B it varied within a 250-1500 msec interval (n = 26). Neurons with the decay time constant of 1500-5000 msec formed subgroup 2A (n = 11), while cells with the longest current decay were include in subgroup 2B (t > 5000 msec, n =7). Cells of group 3, in which the currents demonstrated biexponential desensitization kinetics, had τ of the fast exponent equal to 200-600 msec (n = 21). Under conditions of application of 100 μM ketanov, the decay time constant of рН-induced currents in most DRG neurons examined decreased by 15-20%. In neurons of subgroup 2A (with decay of monoexponential currents with τ = 1500-5000 msec), currents under the action of 100 μM ketanov demonstrated not only acceleration of desensitization by 10-20%, but also a drop in the amplitude by 12‑22%.