Fig. 9. The effect of NaNP (10^-6 mol l^-1, N=6) and L-NAME (3x10^-4 mol l^-1, N=5) on the longitudinal smooth muscles of the proximal intestine of Xenopus laevis. Neither NaNP nor L-NAME had any effect on the force developed by the intestine. 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).