Mechanisms of chronotropic effects of volatile inhalation anesthetics.

The chronotropic effects of all currently available volatile anesthetics were investigated in isolated rat atrial preparations. Anesthetic ethers, diethyl ether, methoxyflurane, and enflurane elicited a dose-dependent positive chronotropic effect. Fluroxene produced a slight depression at low concentrations. The halogenated hydrocarbon anesthetics, halothane, chloroform, and trichloroethylene, did not show a uniform pattern. Halothane's effect was small and biphasic. Chloroform caused a dose-dependent decrease in heart rate, and trichloroethylene caused a marked positive chronotropic effect. The dose-response curves in all anesthetics remained unaltered in the presence of either 3 x 10(-7) M dl-propranolol or 1 x 10(-6) M atropine. It is concluded that volatile anesthetics elicit significant direct chronotropic actions on rat atrial preparations. The mechanism of their actions does not involve stimulation of beta-adrenergic or cholinergic receptors.