Actions of Lidocaine on Atrial and Nodal Transmembrane Potentials in Guinea Pig and Rabbit.

摘要

Effects of lidocaine (1/100,000 M to 4/100,000 M) were determined on transmembrane potentials recorded in guinea pig left atrium and in sinoatrial and atrioventricular nodes of the rabbit heart. The first time derivative of the action potential was displayed as a function of membrane voltage, forming a phase-plane trajectory. A number of parameters of the action potential were determined from the trajectory. Lidocaine reduced the maximum rate of rise of the atrial potential and slowed repolarization. Propagation velocity was reduced, as was maximum ionic conductance. These effects were markedly dependent on the stimulation rate. Variation in the external K(+) and Ca(2+) levels also altered the response to lidocaine. However, relative to appropriate controls these effects were still seen. Atrioventricular nodal potentials were slightly depressed: at 5 Hz the node showed 2:1 block, and perinodal cells were recruited to the functional node. The sinoatrial node showed a decrease in the rate of slow diastolic depolarization, and a slight decrease in spike height. (Author)