EXTRACELLULAR PANCURONIUM AFFECTS SODIUM CURRENT IN CHICK-EMBRYO SENSORY NEURONS

1 The action of pancuronium on transmembrane sodium conductance was in vestigated in dorsal root ganglion neurones of chick embryos. The Nacurrent was measured by use of the patch-clamp technique in whole-cell configuration. 2 Externally perfused pancuronium (50 mu M to 1mM) rev ersibly inhibited the current by a fast mechanism of action. Inhibitio n was concentration-dependent (with a half-effective dose of 170 mu M) but not voltage-dependent. 3 The activation and inactivation kinetics of the Na+ current were estimated in pancuronium and in control solut ion by fitting experimental data with a Hodgkin-Huxley theoretical mod el. 4 The activation time constant tau(m), at negative membrane voltag es, was larger in the presence of pancuronium than in the control. In contrast, the inactivation time constant tau(h) was smaller during dru g perfusion at membrane voltages < - 10 mV. The steady-state inactivat ion h infinity was not affected by pancuronium. 5 These results sugges t that pancuronium may reduce the sodium current by interacting with t he sodium channels in both the resting and open states.