Local anesthetics achieve conduction blockade by targeting which ion channel?

Local anesthetics achieve conduction blockade by targeting which ion channel?

• A. Sodium channel
• B. Potassium channel
• C. Calcium channel
• D. Chloride channel

Answer: (A)

Local anesthetics block conduction by inhibiting voltage-gated sodium channels in nerve membranes. The rapid depolarization that underlies the action potential relies on an inward sodium current through these channels; when they’re blocked, the rising phase of the action potential is blunted or prevented, so the nerve cannot generate or propagate impulses. These drugs access the intracellular side of the channel and preferentially bind to channels that are open or inactivated, producing a use-dependent effect—firing nerves shorten the time to block. Since the primary mechanism of nerve conduction involves sodium influx, blocking this current stops the impulse from traveling along the axon. Potassium, calcium, and chloride channels play other roles (repolarization, neurotransmitter release, and membrane stabilization), but they are not the main targets for producing conduction blockade.

Local anesthetics block conduction by inhibiting voltage-gated sodium channels in nerve membranes. The rapid depolarization that underlies the action potential relies on an inward sodium current through these channels; when they’re blocked, the rising phase of the action potential is blunted or prevented, so the nerve cannot generate or propagate impulses. These drugs access the intracellular side of the channel and preferentially bind to channels that are open or inactivated, producing a use-dependent effect—firing nerves shorten the time to block. Since the primary mechanism of nerve conduction involves sodium influx, blocking this current stops the impulse from traveling along the axon. Potassium, calcium, and chloride channels play other roles (repolarization, neurotransmitter release, and membrane stabilization), but they are not the main targets for producing conduction blockade.