Interference of pentobarbital and verapamil with the reactivity of middle cerebral artery of cat exposed to experimental subarachnoid hemorrhage.

1. Pentobarbital and verapamil produced concentration-dependent vasodilation in segments of middle cerebral artery of either control or exposed to experimental subarachnoid hemorrhage (SAH) cats precontracted with 5-hydroxytryptamine (5-HT, 10(-5) M) or K+ (75 mM), the potency to evoke relaxation being greater for verapamil than pentobarbital. 2. Pentobarbital (10(-4) M and 10(-3) M) or verapamil (10(-6) M) inhibited the contractions induced by 10(-5) M 5-HT or 75 mM K+ in both kinds of vessels. 3. Pentobarbital (10(-3) M) and verapamil (10(-6) M) reduced the concentration-dependent contractions induced by Ca2+ addition in control and SAH arteries previously exposed to Ca2+-free medium containing K+ or 5-HT. 4. All these vasodepressor effects of pentobarbital and verapamil were similar in control and SAH vessels, suggesting that the sensitivity of them to these agents is unaffected by SAH.