Interactions of chlordecone (kepone) and mirex with the nicotinic acetylcholine receptor--ion channel complex

Interactions of chlordecone (kepone) and mirex with nicotinic acetylcholine (ACh) receptor complexes from Torpedo californica electric organs were studied using biochemical probes for ACh and ion-channel binding sites. Neither compound inhibited the binding of [125I] alpha-bungarotoxin (BGT) to the receptor; chlordecone, however, enhanced carbamylcholine affinity for the receptor 5-fold. Chlordecone, but not mirex, also inhibited the binding of [3H]perhydrohistrionicotoxin and [3H]phencyclidine to sites associated with the receptor-gated ion channel. Ion-channel inhibition by chlordecone was enhanced in the presence of carbamylcholine. These results indicate that chlordecone, but not mirex, interacts with the ion-translocation mechanism associated with nicotinic ACh receptors, where it may sterically block ion flux as well as stabilize a desensitized conformation of the receptor complex.