[The effect of local anesthetics on the isolated human right atrial appendages--Part 2: Bupivacaine is different from lidocaine concerning the mechanism of inhibition of contractility].

With regard to the inhibition of contractility, dose-response curves of ryanodine and nickel were produced, and in these curves ID50 values were 10(-6) M and 2 x 10(-3) M, respectively. ID50 of bupivacaine was similar to ryanodine's and that of lidocaine was between ryanodine and nickel. On the post-rest potentiation (PRP) elicited after 2 s of rest following a train of stimulation at 3 Hz, ryanodine and bupivacaine had similar depressing effects, but lidocaine depressed it moderately and nickel showed no effect. These results suggest that bupivacaine could cause a direct inhibitory effect on sarcoplasmic reticulum (SR) function like ryanodine, but lidocaine could cause mainly a reduction in trans-sarcolemmal Ca influx and induce a slight inhibitory effect on SR function.