Actions of trihexyphenidyl and benztropine on squid axon membranes

Trihexyphenidyl and benztropine have potent local anesthetic action on squid axon membranes. They suppress the peak transient sodium conductance with ED50 values equal to 1.75 X 10(-4) AND 0.78 X 10(-4) M, respectively, and shift the sodium condu-tance curve along the potential axis in the direction of depolarization by 2.3 and 8.7 mV, respectively. The time for the sodium current to attain its peak is shortened. Steady-state potassium conductance is also suppressed by these drugs and undergoes an inactivation which has a potential-dependence characteristic. The local anesthetic action combined with the anticholinergic action may warrant further study of these two drugs, especially trihexyphenidyl, as a potential antiarrhythmic agent.