Dieldrin and picrotoxinin modulation of GABA(A) receptor single channels.

The insecticide dieldrin is known to suppress the GABA(A) receptor-channel complex in a manner similar to that of picrotoxin. To elucidate the more detailed mechanisms of dieldrin and picrotoxin interactions with the GABA system, single-channel patch clamp experiments were performed using rat dorsal root ganglion neurons in primary culture. Dieldrin did not alter the open time distribution and mean current amplitude or the distribution of burst duration and the mean burst duration. However, the mean closed time was prolonged indicating that dieldrin decreased the channel open probability. Previous studies have demonstrated that dieldrin and picrotoxin share the common binding site on the GABA receptor. Thus, the effects of picrotoxinin on the GABA(A) receptor single channels were also examined. Dieldrin and picrotoxinin had similar effects at the single-channel level. These changes of single-channel parameters explain the suppressive effects of these chemicals on GABA-induced whole-cell currents.