PK 11195 antagonism of pyrethroid-induced proconvulsant activity

The acute administration of 1R,cis, alpha S-cypermethrin, deltamethrin fenvalerate and permethrin produced a dose-dependent lowering of the dose of pentylenetetrazol required to elicit a seizure in rats. The proconvulsant action of cypermethrin displayed stereospecificity in that the 1R, cis, alpha S isomer of cypermethrin was the most potent compound tested, while the non-insecticidal isomer, 1S,cis, alpha R-cypermethrin, was devoid of proconvulsant activity. Pretreatment of rats with PK 11195, an antagonist of the peripheral-type benzodiazepine binding site, elicited a complete reversal of the proconvulsant actions of both deltamethrin and permethrin. In contrast, pretreatment with phenytoin did not alter the pyrethroid-induced proconvulsant activity. These results suggest that the effects of pyrethroids on pentylenetetrazol seizure threshold are mediated via an interaction with peripheral-type benzodiazepine binding sites.