The tropolonic alcaloid colchicine significantly reduces the behavioural, electroencephalographic and histological damage seen after a 6-min occlusion of the two common carotid arteries of the Mongolian gerbil if the compound is administered at 2 or 4 mg/kg i.p. immediately upon reperfusion. A 45% increase in nigh-frequency ECoG activity and significant reduction of 80% in the hypermotility of the gerbils, with 63% less faults in a passive avoidance paradigm, were observed in conjunction with considerable protection of the hippocampus, after a single dose of 4 mg/kg colchicine. No adverse effects of colchicine treatment on animal movement and body weight were observable. Colchicine's possible mode of action, via inhibition of cellular transport systems, is