Fig. 6. Effects of BRL₃₇₃₄₄ (10 nmol l^-1) before and after treatment with L-N⁵-(1-iminoethyl)ornitine (L-NIO; 10 µmol l^-1), haemoglobin (Hb; 1 µmol l^-1), 1H-(1,2,4)oxadiazolo-(4,3-a)quinoxalin-1-one (ODQ; 10 µmol l^-1) and KT₅₈₂₃ (100 nmol l^-1) on stroke volume (V_S) and stroke work (W_S) in isolated and perfused paced eel hearts. Percentage changes were evaluated as means ± s.e.m. (N=7-8 experiments for each drug). One-way ANOVA was used for comparisons within groups; significance of differences from control values ^*P<0.05. Comparison between groups (two-way ANOVA, Duncan's test) P<0.05.