Objective To investigate the effect of carboxymethyl chitosan on sodium currents (I_(Na)) in single ventricular myocyte of rat,and to explore the mechanism of carboxymethyl chitosan at the ionic channel level.Methods Single ventricular myocyte of rat was isolated with enzymatic dissociation technique.Whole-cell patch clamp technique was used.The stimulating protocol was:holding potential—120 mV,command potential—80 mV to +20 mV,step potential 10 mV,duration 50 ms,stimulating interval 2 s.Results Carboxymethyl chitosan inhibited sodium channel in a dose-dependent manner.When holding potential was—120mV,carboxymethyl chitosan(0.1%,0.2%,0.3%) decreased the peak amplitude of I_(Na) density to 57.4%?6.7%,40.9%?5.4%and 16.1%?4.3%(P