The effects of the optical isomers of propranolol on functional refractory period in rat isolated myocardium.

The two optical isomers of propranolol caused a concentration-dependent increase in functional refractory period of the rat isolated left atrium. In this property the isomers were equipotent. Naradrenaline (1 X 10-(7) M) decreased the functional refractory period. This effect was completely reversed by (-)-propranolol. The (+)-isomer was much less potent than (-)-propranolol in antagonizing the effects of noradrenaline on functional refractory period.