Inhibition of human TREK-1 channels by bupivacaine

Human TWIK-related K+ channels (TREK-1) stabilize the membrane potential (mp) of neurons and have a major role in the regulation of membrane excitability. In view of their physiological significance, interaction of bupivacaine with TREK-I channels may be clinically important. Our aim was to characterize with the patch-clamp technique the properties of human TREK-I channels and the effects of bupivacaine on these channels expressed in Chinese hamster ovary (CHO) cells. Transfection of CHO cells with TREK-1 channels (CHOTREK-1 cells) hyperpolarized the mp from -33 +/- 13 to -78 +/- 4 mV. The channels were stimulated by intracellular acidosis. Inhibition of TREK-I channels by bupivacaine was reversible, concentration-dependent, voltage-independent, and increased with intracellular acidosis. Bupivacaine depolarized the mp of CHOTREK-1 cells in a reversible and concentration-dependent manner. Concentrations for channel inhibition and membrane depolarization were not linearly related (50% inhibitory concentration value for channel inhibition 370 +/- 20 muM, Hill coefficient 1.8 +/- 0.1, n = 51; 50% inhibitory concentration value for membrane depolarization 856 +/- 14 muM, Hill coefficient 2.4 +/- 0.1, mean +/- SEM, n = 27). The results suggest that protonated bupivacaine elicits the observed effects via a site of interaction accessible from the intracellular space. Inhibition of TREK-1 channels and consecutive depolarization of the cell membrane by bupivacaine may contribute to blockade of neuronal signal conduction during regional anesthesia.