The electrophysiological actions of phenylephrine on the rabbit S-A node.

This study characterizes the electrophysiologic effects of the alpha agonist phenylephrine on the rabbit sinus node. Phenylephrine increased sinus node firing rate and increased slope of Phase 4 depolarization. It shortened action potential duration. It had no effect on maximum diastolic potential or action potential amplitude. These actions were blocked by propranolol. These data imply phenylephrine may exert an effect on the sinus node through a beta-adrenoreceptor.