Verapamil aggravates hyperkinesia produced by intrastriatal administration of picrotoxin in rats.

The effects of slow Ca2+ channel blocker verapamil and Ca2(+)-binding agent EDTA were studied on the model of choreic hyperkinesia induced by chronic intrastriatal microinjections GABAA receptor antagonist picrotoxin. Normal and pathological movements were recorded. The test preparations facilitated the effect of picrotoxin on spontaneous and learned behavior. They exerted a permissive effect on picrotoxin-induced hyperkinesia: increase reproducibility and duration of hyperkinesia and decrease the latency of this reaction. Our results indicate that Ca2+ channels are involved into the development and progression of hyperkinesia.