Similarities between the effects of lindane (γ-HCH) and picrotoxin on ligand-gated chloride channels in crayfish muscle membrane

Effects of lindane (γ-HCH) and picrotoxin have been tested on excised outside-out patches of crayfish stomach muscle membrane. The pulsed application of 10^-3 M γ-aminobutyric acid (GABA) elicited an inward Cl^- current of several 100 pA, which could be reversible reduced by the simultaneous application of lindane or picrotoxin. The rise time and desensitization time constant of the GABA response did not seem to be affected. The apparent K_t was 5×10^-6 M for picrotoxin. Also Cl^- currents induced by glutamate or acethylcholine could be reversibly reduced by lindane or picrotoxin. The evaluation of single Cl^- channel openings which were elicited by the simultaneous application of glutamate and lindane showed no effect of lindane on the unitary conductance and on the mean open time of these channels. A mechanism for the antagonistic action of lindane and picrotoxin is discussed.