Fig. 2. Effect of morphine on L-type Ca2+current (ICa.L). ( A ) ICa.Ltraces recorded in a representative myocyte using 300-ms steps to between −40 and +60 mV from −50 mV as shown in the inset during control, after the application of 0.1 μm morphine for 6 min, and after washout of the drug for 10 min. ICa.Lwas increased by the application of 0.1 μm morphine and was partially reversed by drug washout. ( B ) Current–voltage relations of ICa.Ldensity (n = 12) in the absence (control; open circles ) and presence of 0.1 μm morphine ( filled circles ). Data are expressed as mean ± sd. * P < 0.05 versus control. ( C ) Concentration–response relation of morphine effect on ICa.L. Numbers within parentheses are number of experiments.