Which of the following is the mechanism of action of local anaesthetic?
preventing channel activation and inhibiting the Na influx associated with membrane depolarization. Local anesthetic binding to Na channels does not alter the resting membrane potential. With increasing local anesthetic concentrations, an increasing fraction of the Na channels in the membrane bind a local anesthetic molecule and cannot conduct Na ions. As a consequence, impulse conduction slows, the rate of rise and the magnitude of the action potential decrease, and the threshold for excitation and impulse conduction increases progressively. At high enough local anesthetic concentrations and with a sufficient fraction of local anesthetic-bound Na channels, an action potential can no longer be generated and impulse propagation is abolished. Ref: Butterwoh IV J.F., Butterwoh IV J.F., Mackey D.C., Wasnick J.D., Mackey D.C., Wasnick J.D. (2013). Chapter 16. Local Anesthetics. In J.F. Butterwoh IV, J.F. Butterwoh IV, D.C. Mackey, J.D. Wasnick, D.C. Mackey, J.D. Wasnick (Eds), Morgan & Mikhail's Clinical Anesthesiology, 5e.
Block Na+ channel
Block K+ channel
Open Na+ channel
Block Ca++ channel