Fig. 3. Responses to ATP in stomach muscle preparations. (A) Concentration-dependent mean force response to ATP. A statistically significant decrease was obtained at 3 µmol l^–1 in prometamorphosis (N=10) and at 300 µmol l^–1 in juveniles (N=10). There was no effect in metamorphic tissues (N=8). Control value prior to administration of agonist is denoted C. Statistical analysis was performed using repeated measures one-way ANOVA followed by Dunnett's post hoc test. (B,C) Representative traces of the response to ATP in (B) prometamorphic tissues and (C) juvenile tissues (concentrations are in µmol l^–1). (D) Representative trace of the response to a single high concentration of ATP (1000 µmol l^–1).