State-Dependent Inhibition of Sodium Channels by Local Anesthetics: A 40-Year Evolution

Area of Science:

• Neuroscience
• Pharmacology
• Molecular Biology

Background:

• Local anesthetics (LAs) are crucial for pain management and cardiac rhythm control.
• Understanding their mechanism at the sodium (Na+) channel level is key to optimizing their use.

Purpose of the Study:

• To review the evolving knowledge of local anesthetic impulse blockade mechanisms.
• To identify molecular targets and binding states of local anesthetics within Na+ channels.

Main Methods:

• Review of decades of research on local anesthetic-Na+ channel interactions.
• Analysis of molecular models and experimental data on binding sites and affinity.

Main Results:

• Local anesthetic binding to Na+ channels is state-dependent, with varying affinity for resting, open, and inactivated states.
• Specific amino acid residues, particularly on S6 segments and selectivity filter, are implicated in binding.
• Binding sites may exhibit flexibility, with different residues involved in binding to different channel states.

Conclusions:

• The molecular understanding of local anesthetic action has advanced significantly.
• State-dependent binding and specific molecular interactions explain therapeutic and toxic effects.
• Further research is needed to elucidate gating charge inhibition and hydrophobic pathway roles.