The effect of bupivacaine on tetrodotoxin-resistant and tetrodotoxin-sensitive sodium channels in rat dorsal root ganglion neurons

Objective To investigate the effect of bupivacaine on tetrodotoxin(TTX)-sensitive(S) and tetrodotoxin-resistant(R) sodium channels and to further evaluate the mechanism of bupivacaine.Methods The dorsal root ganglion(DRG) neurons of the thoracic and lumbar segments in Sprague-Dawley rats(one month) were isolated acutely.Under the condition of holding voltage -100mv and -90mv,testing voltage -10mv and 0mv with duration of 50ms and 100ms,the whole-cell patch clamp technique was applied to recording the changes of voltage-gated TTX-S and TTX-R I Na following the administration of bupivacaine at 0～1000μmol/L.Results Bupivacaine blocked the voltage-gated TTX-S and TTX-R I Na in dose-dependent channel.The IC 50 (17.069μmol/L) of TTX-S I Na was significantly lower than that for TTX-R I Na (IC 50=34.511μmol/L).Conclusion The effects of bupivacaine may account for production by the drug of a differential Na + channel block.