Figure 2.

Effect of the selective and non-selective PDE inhibitors on the inherent tone in passively sensitized human airways. Non-selective PDE inhibition (theophylline, IBMX) as well as the selective PDE3 (motapizone), PDE4 (RP73401, rolipram, AWD 12-281), and PDE3/4 inhibition (motapizone+RP73401, zardaverine) significantly relaxed bronchial rings compared to the respective solvent controls, while adenosine receptor antagonism (8-phenyltheophylline) had no significant effect. Responses of the PDE inhibitors were not significantly different from the effect of isoprenaline, whereas 8-phenyltheophylline was significantly less effective. Overall there was no significant difference between the relaxing effects of the different drugs including 8-PT (ANOVA). ^*P<0.05 in comparison with the solvent control, #P<0.05 in comparison with isoprenaline.