Figure 4. Inhibition by ICI204448 and asimadoline of cholinergically-mediated, EFS-evoked contractions of human isolated colon in the presence of L-NAME 300 μM.

Representative trace examples are shown for ICI 204448 (panel A) and asimadoline (panel B). The concentration-response relationships for the inhibition of contractions by ICI204448 and asimadoline are shown in panel C for the ascending and in panel D for descending colon. Panel E shows the effect of pre-incubation of the kappa opioid receptor antagonist norbinaltorphimine 3–300 nM on the concentration-response relationship for the inhibition of contractions by ICI 2044448 in the descending colon. Panel F shows a linear regression of the relationship between log₁₀[norbinaltorphimine] and the dose ratio −1 (DR-1) of the EC₅₀s of ICI 204448 in the presence of 3–300 nM norbinaltorphimine. Data are expressed as means ± SEM; n = 4–6 each concentration or 3–4 each concentration in the experiments with norbinaltorphimine.