Bupivacaine-induced slow-inward current inhibition: a voltage clamp study on frog atrial fibres.
The effects of various concentrations of bupivacaine on the characteristics of the slow-inward current (isi) were studied over a ten-minute period on isolated frog atria. At a concentration of 10(-7) M, bupivacaine did not modify isi. At 10(-6) M, the maximal amplitude of the slow-inward current (i max) was depressed by 11 per cent. At 10(-5) M, i max was depressed by 24.5 per cent, the time-to-peak current value (tpeak) was increased by 13.4 per cent and the inactivation time constant (tau in) by 29.8 per cent. At 10(-4) M, i max was depressed by 32.9 per cent, tpeak increased by 30.4 per cent and tau in by 58.7 per cent. In conclusion, bupivacaine produced only moderate inhibition of the slow-inward current. The findings might explain the decline in sinus impulse formation with sinus bradycardia, and the slowing of atrio-ventricular node conduction produced by bupivacaine. However, the decrease in contractility previously reported does not seem to be due only to inhibition of the slow-inward current.
de La Coussaye
J E
JE
Unité Cardio-vasculaire du Laboratoire, Physiologie I, Faculté de Médecine, Montpellier, France.
Massé
C
C
Bassoul
B P
BP
Eledjam
J J
JJ
Gagnol
J P
JP
Sassine
A
A
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D016275:Atrial Function / Q000187:drug effects*; D001283:Atrioventricular Node / Q000187:drug effects*; D002045:Bupivacaine / Q000494:pharmacology*; D004562:Electrocardiography / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D011898:Ranidae
D002045:Bupivacaine