the neuromodulator, substance p, activates trpc3/7 channels inducing cellular currents that underlie rhythmic pacemaker activity in the brainstem, enhancing the regularity and frequency of respiratory rhythms, showing homology to the mechanism described in bg neurons. transgenic cardiomyocytes expressing trpc3 show prolonged action potential duration when exposed to a trpc3 agonist. the same cardiomyocytes also increase their firing rate with agonist exposure under a current-clamp tetanus protocol suggesting that they may play a role in cardiac arrhythmogenesis.