At greater doses, local anesthetics inhibit which neurons?

At greater doses, local anesthetics inhibit which neurons?

• A. Only central inhibitory neurons
• B. Only central excitatory neurons
• C. Both central inhibitory and excitatory neurons
• D. Peripheral motor neurons

Answer: (C)

Local anesthetics block voltage-gated sodium channels in neurons, preventing action potentials. In the brain, inhibitory interneurons are blocked first, which reduces the normal braking on neural activity and can produce seizures due to disinhibition. As the dose increases, the blockade extends to excitatory neurons too, so both central inhibitory and central excitatory neurons are inhibited. This broader suppression leads to CNS depression at higher systemic levels. Peripheral motor neurons aren’t the primary site for this dose-dependent CNS effect, so the key idea is that both central inhibitory and excitatory neurons are inhibited at greater doses.

Local anesthetics block voltage-gated sodium channels in neurons, preventing action potentials. In the brain, inhibitory interneurons are blocked first, which reduces the normal braking on neural activity and can produce seizures due to disinhibition. As the dose increases, the blockade extends to excitatory neurons too, so both central inhibitory and central excitatory neurons are inhibited. This broader suppression leads to CNS depression at higher systemic levels. Peripheral motor neurons aren’t the primary site for this dose-dependent CNS effect, so the key idea is that both central inhibitory and excitatory neurons are inhibited at greater doses.