Modification of pattern of excitatory junction currents in the guinea pig vas deferens by the gap junction uncoupler heptanol

Extracellularly recorded excitatory junction currents (EJCs) produced by neurotransmission to the smooth muscle of the vas deferens have a varied phasic composition. They can be positive going (p-EJC), negative going (n-EJC) or biphasic (b-EJC) from one event to the next. The phasicity is believed to depend upon the syncytial properties of the smooth muscle cells. The authors have investigated the effects of 1-heptanol, an intercellular uncoupling agent, on the phasicity of EJCs. In control Krebs solution EJCs with a positive phase (p- and b-EJCs) occurred as a considerable fraction of total EJCs recorded. Following the application of 2 mM heptanol for 2-3 min., the occurrence of p-and b-EJCs decreased markedly while that of n-EJCs increased. The change was reversible and repeatable. Heptanol did not, however, affect the prejunctional nerve action potential. These bioelectric results can be explained in terms of the specific uncoupling of smooth muscle cells by heptanol.