Overview
- Hanson, I.R. et al. (1950) Curr. Res. Anesth. Analg. 29, 136.
- Weiser, T. (2006) Neurosci. Lett. 395, 179.
Alomone Labs Lidocaine inhibits NaV1.2 channels expressed in Xenopus oocytes.A. Currents were elicited by a double test pulse protocol applied every 10 sec, which is schematically described on the top panel. For the first pulse the holding potential was -120 mV while the second pulse was preceded by 100 ms at -80 mV. On the bottom; superimposed example current responses to the voltage stimulation, before (black) and during application of 0.5 mM Lidocaine (#L-105), (green). B. Time course of NaV1.2 current amplitude changes as a result of Lidocaine application, for each of the two test pulses (demonstrating the dependency of the inhibition on the voltage driven conformation of the channel).
Voltage-gated Na+ channels (VGSC, NaV) are critically important for electrogenesis and nerve impulse conduction, and are targeted by clinically relevant analgesics such as Lidocaine1. Certain NaV channel isoforms are predominantly expressed in peripheral sensory neurons associated with pain sensation, and the expression and functional properties of these channels can be dynamically regulated following axonal injury or peripheral inflammation2.
Lidocaine is a commonly used local anesthetic as well as an antiarrhythmic drug, which is a potent and selective blocker of NaV channels3. It inhibits, for instance, human NaV1.5 channels expressed in Xenopus oocytes in a positive rate-dependent and concentration-dependent manner, with an IC50 value of 145.6 µM4. Its block can be complex, exhibiting channel state-dependent and time-dependent elements5.
Reports on the effects of Lidocaine suggest that although the drug is somewhat selective in voltage-clamp experiments (the drug blocks TTX-sensitive currents at concentrations that are approximately fourfold lower than those that block high-threshold TTX-resistant currents), its functional discrimination is likely to be poor. Lidocaine block of TTX-sensitive currents indicates an IC50 value between 40 and 50 µM using protocols that incorporate a negative holding potential6-7. This block of high-threshold TTX-resistant currents has a reported IC50 of approximately 200 µM using similar protocols. The channel state-dependence of TTX-resistant current block has been demonstrated by a depolarization that maximally activates the current. Under these circumstances the IC50 decreases to 60 µM.6-7
