Cardiovascular actions of optical isomers of propranolol

Effects of the optical isomers of propranolol on blood pressure in the rat, and in the spinal rat during adrenaline infusion were studied to investigate the mechanism of the pressor action of propranolol. Both isomers of propranolol produced a sustained pressor action in the rat and in the spinal rat infused with adrenaline. The magnitude of the pressor action produced by the d- and 1-propranolol was proportional to their beta-adrenoceptor blocking activities in the heart as was reported by several investigators. It is concluded that the pressor action of propranolol is due to the blockade of the beta-adrenoceptors mediating vasodilation in the skeletal muscle vascular beds.