Effects of lidocaine in rabbit atria

Standard microelectrode recordings were obtained from rabbit right and left atria. Lidocaine (1 X 10(-5) M) had no effect on these, but 5 X 10(-5) M lidocaine significantly slowed rate and Vmax. This concentration had no effect on the duration of the action potential, a result clearly different from the effect of this drug in Purkinje tissue. Lidocaine had much less effect on the 'steady-state' relation of membrane potential to Vmax of phase 0 of the action potential than on the 'membrane responsiveness curve' obtained by the extra stimulus technique. We have demonstrated time-related recovery from sodium inactivation in rabbit left atria and have shown that lidocaine slows recovery in this tissue as it does in Purkinje fibres.