Comparison of blocking effect of ropivacaine and bupivacaine on sodium channels of rat dosal root ganglia / 中国临床药理学与治疗学

ABSTRACT

AIM: To compare the blocking effect of ropivacaine and bupivacaine on sodium channels of rat dosal root ganglia(DRG) using whole cell recording technique. METHODS: Rat DRG neurons were enzymatically isolated , tetrodotoxin-sensitive(TTX-s) and tetrodotoxin-resistant (TTX-r) sodium currents of DRG were recorded by whole cell recording.Drugs were given in bath solution.The concentrations of ropivacaine were 10,30,100, 1 000 ?mol?L~ -1 and bupivacaine were 10,30,100,300 ?mol?L~ -1 . The recording number in each dose group was six. RESULTS: CsCl in extracellular fluid and TEA in intracellular fluid were used to block the potassium channels. Sodium currents were recorded when the holding potential was - 70 mV and a serials of pulse with step 10 mV and duration 70 ms was given.TTX-s sodium channel was recorded in 80.1 % large DRG cells and TTX-r sodium channel was recorded in 92.4 % medium and small DRG cells,of which 56.3 % cells had no response to 1 ?mol?L~ -1 TTX. The half-maximal blocking concentrations of ropivacaine on TTX-r sodium channel was 65.7 ? 6.1 ?mol?L~ -1 , which was much lower than that on TTX-s sodium channel 246.8 ? 11.2 ?mol?L~ -1 (P 0.05 ). CONCLUSION: Ropivacaine preferentially blocks TTX-r sodium channel.Selective blocking of TTX-r and TTX-s sodium channel was one of the reasons of seperation of sensation and motion when it is used in epidural anesthesia.