Effects of carbachol on EFS-induced contractions of left atria from
wild-type (DDY) mice. A, typical traces of inotropic responses to 10 nM, 100
nM, 1 μM, 10 μM, and 100 μM carbachol applied noncumulatively. B,
typical traces of inotropic response to carbachol applied cumulatively at
3-min intervals (10 nM, 100 nM, 1 μM, 10 μM, and 100 μM). C, time
course of inotropic responses to carbachol (300 nM, 1 μM, 3 μM, 10
μM, and 30 μM). Ordinate, relative amplitude of EFS-induced contraction
expressed as a percentage of the amplitude just before application of
carbachol. Abscissa, incubation time with carbachol. D, comparison of
concentration response curves for carbachol constructed from cumulative
(▪) and noncumulative application of carbachol (•). Ordinate,
relative amplitude of EFS-induced contraction expressed as a percentage of the
amplitude just before application of carbachol. Abscissa, concentration of
carbachol (log M). Values are means and S.E.M. of five to six experiments.