8-Bromo-cyclic GMP abolishes TEA-induced slow action potentials in canine trachealis muscle.

Using intracellular microelectrodes, we investigated whether 8-bromo-guanosine 3':5'-cyclic monophosphate (cGMP) influenced the electromechanical effects of tetraethylammonium (TEA) on canine tracheal smooth muscle. We found that 20 mM TEA depolarized airway smooth muscle cells from -58 +/- 3 mV (means +/- S.D.) to -44 +/- 2 mV and caused spontaneous action potentials (APs) to develop which were 31 +/- 2 mV in amplitude. These APs, and the phasic contractions electrically coupled to them, were totally abolished in buffer containing 0.1 mM cGMP. Our findings suggest that cGMP markedly affects the channels mediating TEA-induced APs in airway smooth muscle.