Chloride channel

Abstract

Cl^- current in GABA-sensitive neurons of the frog dorsal root ganglia was separated from other Na⁺, Ca²⁺ and K⁺ currents using the suction pipette technique which allows internal perfusion and current clamp. Adequacy of the internal perfusion technique was assessed from the reversal potential for GABA-induced Cl^- current (E_GABA) at various intracellular Cl^- concentrations. E_GABA was equal to the Cl^- equilibrium potential (E_c1) and behaved as a simple Cl^- electrode following changes of external and internal Cl^- concentrations ([Cl]₀ and [Cl]₁). E_GABA changed by 58 mV for a tenfold change in either [Cl]₀ or [Cl]_i at constant [Cl]₀ or [Cl]₁, respectively. GABA-induced Cl^- conductance increased dose-dependently. In addition, single Cl^- channel current (i_cl) and conductance (γ_c1) were estimated from the Cl^- current fluctuation by using both power spectrum and amplitude histogram methods, and the theoretical values were compared with those measured directly by a conventional inside-out patch clamp technique.