Evidence for greater susceptibility of isolated dog cerebral arteries to Ca antagonists than peripheral arteries.

In helically-cut strips of dog cerebral, coronary and mesenteric arteries, contracted with prostaglandin (PG) F2 alpha or K+, the addition of verapamil caused a dose-related relaxation. Verapamil-induced relaxations were greater in cerebral than in the other arteries when contracted with PGF2 alpha, but did not significantly differ in the arteries contracted with K+. Similar results were obtained with diltiazem and nifedipine. The contractile response to PGF2 alpha was attenuated by pretreatment with verapamil, the ateenuation being greater in cerebral than in mesenteric arteries. Nitroglycerin and sodium nitroprusside relaxed cerebral, coronary and mesenteric arteries contracted with PGF2 alpha to a similar extent. It may be concluded that dog cerebral arteries contracted with PGF2 alpha, one of endogenous vasospastic substances, are more susceptible to agents which interfere with the influx of Ca++ across cell membranes than coronary and mesenteric arteries; these agents may thus be of value in the treatment and prophylaxis of cerebral vasopasm.