Figure 4. The effect of L-type calcium channel blockade by 10 sup -7 M D888 on the vasorelaxing effect of S(+) ketamine ([circle, open]) and R(-) ketamine ([round bullet, filled]) on norepinephrine-contracted, N sub omega -nitro-L-arginine-pretreated aortic rings. Data are given as means +/- SEM. Parentheses indicate the number of preparations studied. For half-maximum effective concentration values, see Table 2.