gamma-Aminobutyric acid-induced depression of calcium currents of chick sensory neurons.

The effects of gamma-aminobutyric acid (GABA) on calcium currents were investigated in avian dorsal root ganglion (DRG) cells. GABA was applied to the vicinity of the cells by ejection pipettes using constant-pressure pulses. GABA concentrations between 5 and 100 mu M reduced and slowed the calcium current in a dose-dependent manner. A contribution of K and Cl outward currents to the reduction of the inward current was minimized by using identical caesium chloride concentrations on both sides of the membrane. The onset of the effect was rapid and 80% of the effect was observed within 1 s. The attenuation of the Ca slope conductance by GABA was found to be independent of the membrane potential between -50 and +50 mV.