국소마취제의 전압의존성 칼슘전류 억제효과 ; 역가와 혐수성과의 상관관계

Background : The primary mode of conduction blockade by local anesthetics occurs through the inhibition of voltage-dependent sodium current and, inhibitory potency of local anesthetics are correlated with their hydrophobicity, expressed as octanol/buffer partition coefficients(PC). The homologous structural biochemistry and analogous physiology of voltage-dependent sodium and calcium channels prompted us to examine the relationship between potency of various local anesthetics for the inhibition of voltage-dependent calcium channels(VDCC) and their PC values. Methods: Whole cell patch clamp recordings were made from acutely dissociated rat dorsal root ganglion neurons, and voltage dependent calcium current(ICa) was evoked by depolarizing pulse. The concentrations of various local anesthetics(bupivacaine, lidocaine, prilocaine, procaine, tetracaine) that block 50% of the control ICa(IC50) were calculated from dose-response curves. The relationship between IC50 and PC values of various local anesthetics were investigated. Results : Local anesthetics inhibited ICa with neglegible effect on the current- voltage relatonship. IC50 values of tetracaine, bupivacaine, lidocaine, prilocaine and procaine were 98, 142, 2710, 10400, 16900 uM respectively, and linear regression of the plot of log(IC50) against log(PC) was statistically significant (p＜0.001). Conclusions : It is speculated that inhibitory effects of local anesthetics on the VDCC when used in epidural and spinal anesthesia may contribute to their analgesic and anesthetic actions. Inhibitory potency of local anesthetics on the VDCC, as for voltage-dependent sodium channels, was correlated with their hydrophobicity. (Korean J Anesthesiol 1998; 34: 486∼492)