Characterization of gamma-aminobutyric acid responses with sulfate loading in cat bladder neurons

In some cells in cat bladder ganglia gamma-aminobutyric acid (GABA) applied iontophoretically produced a hyperpolarizing response accompanied by an increase in input conductance when recorded with potassium sulfate-filled microelectrodes. This GABA-induced hyperpolarization was blocked by bicuculline and was converted to a depolarizing GABA response when extracellular chloride concentration was low suggesting that the hyperpolarizing GABA response was mediated by the opening of chloride channels. In other cells, continuous passage of a small negative current converted a depolarizing GABA response to a hyperpolarizing response with time. This effect was accompanied by a negative shift of the reversal potential. These data indicated that injection of impermeable sulfate ions decreased the intracellular chloride concentration.