RESUMO
Fifteen min after adding nimodipine 50 ?mol/L, the contractility of the left atrial muscle decreased from 100 % of control to 55.5 +4.2 o/o and its inhibitory effect was equal to the effect of verapamil (25 ?mol/L ) . Nim at the same concentration inhibited strongly the positive staircase phenomenon but could not reverse it into the negative staircase phenomenon as verapamil 25 ?mol/L did. The same concentration of Nim suppressed significantly the post rest contraction. On the contrary, the post rest contraction was not affected by verapamil at 25 ?mol/L. In addition, Nim 50 ?mol/L reversed or prevented significantly the ouabain-induced arrhythmias in isolated left atria. These results suggest that the negative ino-trbpism of Nim may be related not only to the inhibition of Ca2 + influx to the cells and also to the decrease of the intercellular Ca2+ release and that Nim might present the possibility in treating arrhythmias or other heart disease