The inhibitory effects of bupivacaine, levobupivacaine, and ropivacaine on K_2P (two-pore domain potassium) channel TREK-1

Purpose: Bupivacaine, levobupivacaine, and ropivacaine are amide local anesthetics. Levobupivacaine and ropivacaine are stereoisomers of bupivacaine and were developed to circumvent the bupivacaine's severe toxicity. The recently characterized background potassium channel, K_2P TREK-1, is a well-known target for various local anesthetics. The purpose of study is to investigate the differences in inhibitory potency and stereoselectivity among bupivacaine, levobupivacaine, and ropivacaine on K_2P TREK-1 channels overexpressed in COS-7 cells. Methods: We investigated the effects of bupivacaine, levobupivacaine, and ropivacaine (10, 50, 100, 200, and 400 μM) on TREK-1 channels expressed in COS-7 cells by using the whole cell patch clamp technique with a voltage ramp protocol ranging from -100 to 100 mV for 200 ms from a holding potential of -70 mV. Results: Bupivacaine, levobupivacaine, and ropivacaine showed reversible inhibition of TREK-1 channels in a concentration-dependent manner. The half-maximal inhibitory concentrations (IC₅₀) of bupivacaine, levobupivacaine, and ropivacaine were 95.4 ± 14.6, 126.1 ± 24.5, and 402.7 ± 31.8 μM, respectively. IC₅₀ values indicated a rank order of potency (bupivacaine > levobupivacaine > ropivacaine) with stereoselectivity. Hill coefficients were 0.84, 0.93, and 0.89 for bupivacaine, levobupivacaine, and ropivacaine, respectively. Conclusion: Inhibitory effects on TREK-1 channels by bupivacaine, levobupivacaine, and ropivacaine demonstrated stereoselectivity: bupivacaine was more potent than levobupivacaine and ropivacaine. Inhibition of TREK-1 channels and consecutive depolarization of the cell membrane by bupivacaine, levobupivacaine, and ropivacaine may contribute to the blockade of neuronal conduction and side effects.