[Blocking effect of furosemide on the chloride permeability of mollusk neuron membranes induced by acetylcholine and gamma-aminobutyric acid].

Furosemide (2.10(-4) to 1.10(-3) g/ml) was shown to prevent the increase of chloride conductance induced in isolated neurons of freshwater mollusc Planorbarius corneus by ionophoretic application of acetylcholine, suberyldicholine or gamma-aminobutyric acid. Furosemide caused no shift in the reversal potential of the chloride-dependent responses if the experiments were carried out employing microelectrode filled with potassium sulphate. When potassium chloride-filled microelectrodes were used, the reversal potential became less negative in the presence of furosemide. This effect seems to be due to the blocking of the active transport of chloride by furosemide. Neither sodium-dependent, nor potassium-dependent responses induced by cholinoreceptor activation were influenced by furosemide. Furosemide was found to diminish both the amplitude and the rate of chloride-dependent responses. The lack of selectivity with respect to acetylcholine or gamma-aminobutyric acid suggests that furosemide blocks the chloride channels of chemoceptive membrane which are probably common to acetylcholine and gamma-aminobutyric acid and does not affect their receptors.