Effects of acetaldehyde on the membrane resistance in the smooth muscle of the guinea-pig taenia caecum.

The action of acetaldehyde on the membrane resistance of the guinea-pig taenia caecum was investigated with a double sucrose-gap method in different ionic environments. Application of acetaldehyde (10--20 mM) produced hyperpolarization, block of spike discharge and reduction of the membrane resistance. The reduction of the membrane resistance by acetaldehyde was potentiated by increasing the external K+ concentration and by replacement of Cl- with NO3-; it was reduced by lowering the external K+ concentration and by replacement of Cl- with benzenesulfonate. Replacement of NaCl with Tris-Cl, sucrose, or LiCl had no appreciable effect on the action of acetaldehyde on the membrane resistance. It therefore seemed likely that acetaldehyde increased the membrane conductance for K+ and Cl- more than for Na+. Although this action of acetaldehyde was similar to the alpha-action of catecholamine, the decrease of the membrane resistance and hyperpolarization induced by acetaldehyde remained unchanged in the presence of phentolamine.