A benzodiazepine antagonist action of CL 218,872.

The effect of the Type I benzodiazepine (BDZ) receptor agonist, CL 218,872, on convulsions generated by low doses of methyl beta-carboline-3-carboxylic acid ( MBCC ), bicuculline, picrotoxin and pentylenetetrazole (PTZ) in mice was examined. Low doses of CL 218,872 enhanced the convulsions produced by all agents except PTZ. An anticonvulsant action of CL 218,872 was observed at higher doses. Since CL 218,872 exhibits proconvulsive effects at low doses, and a proconvulsant action is a characteristic of compounds classified as BDZ antagonists, it appears that CL 218,872 has some antagonist action.