The effects of lofocaine on necotinic acetylcholine reseptors

Nicotinic acetylcholine receptors (nAChR) were expressed in the plasma membrane of Xenopus oocytes following microinjection with mRNA extracted from denercated and innerated leg muscles of a rat. Whole cell currents, activated by acetylcholine, were recorded, using the voltage clamp method, and the effects of lidocaine on nAChR were examined on the basis of minimm reaction model proposed by Hess and his colleagues. Application of lidocaine (1μM-1mM) 5 min prior to acetylcholine (100μM) administration inhibited responses of nAChR to acetylcholine in concentration-dependent manner. The fraction of inhibition produced by 30μM lidocaine was higher, as acetylcholine concentration was increased. Accrding to minimum reaction model, the inhibition constant of lidocaine for the closed-channel from of nAChR was estimated at 71.6μM, and that for the open-channel from at 21.4μM. The results indicate that lidocaine inhibits nAChR in a concentration-dependent manner, and that its blocking effect is attributed to the interaction of lidocaine with nAChR mainly in the open-channel form.