Cardiovascular and beta-adrenergic blocking effects of timolol

The haemodynamic effects of timolol and its inhibiting action on the cardiovascular and bronchial effects of isoproterenol have been studied. Splanchnic nerve activity was recorded. The antiarrhythmic action of timolol was studied on guinea pig isolated atria, using arrhythmias induced by epinephrine, ouabain or coronary ligation in the dog. Timolol is a very potent beta-adrenoceptor blocking agent, without specificity on beta1- or beta2-receptors. No intrinsic beta-stimulating or depressant effects were found. Timolol reduced splanchnic discharges. The antiarrhythmic effect of timolol was limited to epinephrine-induced arrhythmias.