Effects of amphetamine on calcium and potassium currents in rat heart

We used the patch-clamp technique to study the effects of amphetamine on th e membrane currents responsible for rat cardiac action-potential duration. Amphetamine has no effect on the slow inward Ca2+ current (I-Ca-L), the inw ardly rectifying K+ current (I-K1) and the outward K+ delayed rectifier (I- K) and sustained (I-ss) currents. Amphetamine blocks the transient outward K+ current (I-to) both in the open and in the rested state. The transient o utward K+ current is largely responsible for action-potential repolarizatio n and fur the regional differences in action-potential duration in rat vent ricle. Therefore, the reduction of the transient outward K+ current (I-to) caused by amphetamine may facilitate the appearance of ventricular tachycar dia and fibrillation, a reported cause of death in amphetamine users.