[Mechanisms of action of volatile anesthetics on smooth muscle]

The development of intracellular Ca2+ fluorescent indicators and specific enzymatic substances as well as the application of the patch-clamp method have made it possible to clarify the mechanisms of action of volatile anesthetics inhibit smooth muscle contraction in part by decreasing intracellular Ca2+ concentration ([Ca2+]i); this effect is mediated by blocking calcium channels, especially the L-type voltage-operated channel, and by raising the intracellular cyclic AMP and cyclic GMP levels. Volatile anesthetic-induced suppression of smooth muscle contraction is also attributable to mechanisms independent of [Ca2+]i, which involve the depression of Ca2+ sensitization mediated by C kinase.