The inhibition of sodium channel currents in rat sympathetic ganglion neurons by ropivacaine / 中华麻醉学杂志

ABSTRACT

Objective To investigate the effects of ropivacaine on the whole cell sodium currents in rat sympathetic ganglion neurons in order to determine whether sympathetic ganglion is involved in the ropivacaine cardiotoxity. Methods The sympathetic neurons were enzymatically isolated from the superior cervical ganglion. The effects of ropivacaine on the whole cell sodium channel currents were assessed using patch clamp technique. Results Ropivacaine blocked the whole cell sodium channel currents dose dependently. When the holding potential (Vh) was -80mV and Vt Omv , 0.01?mol/L ropivacaine reduced peak currents by 30.02% with a mean IC50 of 2.68?mol/L. The blockade was also potential dependent. When Vh was -60mv, the mean IC50 was 1.55?mol/l. 1.0?mol/L ropivacaine reduced the peak value of I V curve by 30.66% but did not affect the shape of I V curve and caused 2.56mv shift of voltage dependence activation curve to depolarized potentials and 3.56mv shift of steady state inactivation curve to more hyperdepolarized potentials.The conditioning pulse potential at which half maximal channels were activated (V1/2), changed from -52.99mv to -56.44mv and the test potential at which half maximal channels were activated (V1/2), changed from -25.2mv to -22.64mv. Conclusions Subconvulsive concentration of ropivacaine significantly inhibits sympathetic ganglion neurons in a dose dependent and potential dependent way through the inactivation of sodium channel,indicating that sympathetic ganglion neurons may contribute to the cardiotoxity of ropivacaine.