Which of the following are theories of regional anesthesia

(Ref: Malamed, Ed. 5th Pg-12) * The nerve membrane is the site at which local anesthetics exe their pharmacological actions. The following theories have been given over the years to explain the mechanism of action of local anesthetics- - The Acetylcholine theory. - The Calcium Displacement theory. - The Surface Charge (Repulsion) theory. - The membrane Expansion theory. - The Specific Receptor theory. * The Specific Receptor theory is the most accepted one. It proposes that the local anesthetics act by binding to specific receptors on the sodium channel.