Effects of propofol on contractile response and electrophysiological properties in single guinea-pig ventricular myocyte

Effects of propofol on contractile response, action potential, resting memb rane potential and L-type voltage-dependent calcium channel current were ex amined in guinea-pig single cardiac myocyte. Propofol (10(-4) M) inhibited contractile response induced by electrical stimulation (83.6% of control, n =5), but did not change the resting membrane potential. On the other hand, propofol reduced the overshoot of action potential (10(-4) M), and shortene d the duration of action potential (10(-5) and 10(-4) M). Whole-cell voltag e clamp experiment showed inhibition of L-type calcium channel current (I-C a, 10(-5) M: 90.8+/-1.39, 10(-4) M: 83.4+/-1.53% of control, n=5). In addit ion, propofol showed use-dependent block of I-Ca. It is concluded that nega tive inotropic effect of propofol is caused by suppression of action potent ial, and that inhibition of I-Ca plays a role in shortening of the duration of action potential.