Fig. 5. (A) Concentration-dependent decrease in mean force in response to adenosine. A statistically significant decrease was obtained at 10 µmol l^–1 in prometamorphosis (N=12), at 100 µmol l^–1 in metamorphosis (N=6) and at 300 µmol l^–1 in juveniles (N=12). (B) Concentration-dependent decrease in mean force in response to N⁶-cyclopentyladenosine (CPA) in prometamorphosis (N=8), metamorphosis (N=11) and juveniles (N=10). Statistically significant decrease obtained at 1 µmol l^–1 for all stages. Control value prior to administration of agonist is denoted C on the x-axis. Statistical analysis was performed using repeated measures one-way ANOVA followed by Dunnett's post hoc test (A,B). (C) Effect of adenosine in the presence and absence of the A₁ receptor antagonist DPCPX (1 µmol l^–1) in prometamorphic (100 µmol l^–1 adenosine, N=4) and juvenile (1000 µmol l^–1 adenosine, N=9) stomach muscle strips. Statistical analysis was performed using repeated measures one-way ANOVA followed by Bonferroni's post hoc test. Asterisk indicates P<0.05. (D) Effects of the adenosine kinase inhibitor 4-amino-5-(3-bromophenyl)-7-(6-morpholino-pyridin-3-yl)pyrido[2,3-d]pyrimidine (ABT-702, 1 µmol l^–1) on mean force developed under control conditions in prometamorphic (N=7) and juvenile (N=10) tissues. Statistical significance was calculated using Student's t-test for paired observations. Asterisk indicates P<0.05.