Fig. 7. The effect of NaNP (10^-7 mol l^-1, N=6; 10^-6 mol l^-1, N=8) and L-NAME (3x10^-4 mol l^-1, N=6) on the circular smooth muscles of the cardiac stomach of Xenopus laevis. NaNP reduced the mean force developed while L-NAME enhanced the force developed. The results are presented as mean force developed (± S.E.M.) above resting level. Open bars represent values immediately before addition of drug. ^*P0.05 compared to the control (C).