Effect of acetylcholine on the electrophysiology and proliferative response of human lymphocytes

Using the patch-clamp technique, we determined that 1-15 mM extracellular acetylcholine reduced whole-cell n-type K+ currents in human peripheral blood lymphocytes and accelerated their inactivation. The percentage increase in K+ channel inactivation rate and the degree of drug induced block were independent of membrane potential. In flow cytometric membrane potential measurements with the oxonol dye similar doses of acetylcholine depolarized the lymphocyte population. Both acetylcholine induced K+ channel block and depolarization fully developed within 2 minutes. The depolarizing and K+ channel blocking effects of acetylcholine are in concert. [3H]thymidine incorporation experiments proved that the proliferative response of PHA stimulated peripheral blood lymphocytes was decreased by increasing concentrations of acetylcholine in the 1-50 mM range.