Figure 6. Effect of muscarinic or 5-HT receptor antagonist on PA1-induced HCO₃⁻ secretion.

Muscarinic or 5-HT receptor antagonist was injected i.v. at t = 0 min. PA1 (1 μm)-induced HCO₃⁻ secretion was inhibited by atropine (0.5 mg kg⁻¹) (A), telenzipine or J104129 (1 mg kg⁻¹) (B). C, 5-HT₄ antagonist GR113808 (1 mg kg⁻¹) abolished PA1-induced HCO₃⁻ secretion, whereas 5-HT₃ receptor antagonist ondansetron (1 mg kg⁻¹) had no effect. Each data point represents the mean ± SEM (n = 6 rats). *P < 0.05 vs. pH 7.0 Krebs group. ^†P < 0.05 vs. PA1 group.