Theories of Local Anesthesia

THEORIES OF LOCAL ANAESTHESIA are -
A. Calcium displacement theory:
LA molecules displaces calcium inside the nerve which in turn controls sodium channels.

B. Electrical potential theory: The cations RNH+ of LA align themselves on the nerve membrane and make outside potential more positive, thus the threshold potential is increases.

C. Membrane expansion theory: LA penetrates the membrane, expands it and narrows the sodium channels, thus decreases the permeability to sodium ions.

D. Specific receptor theory: The specific receptors are sodium channels which are bound by LA controls the sodium channels. It is the most acceptable theory which explains the actions of LA.