Fig. 3. (A–E) pH_i changes induced by bath application of 10 mmol l^–1 cAMP (A), 10 µmol l^–1 8-CPT-cAMP (B), 100 µmol l^–1 of the adenylyl cyclase inhibitor forskolin (C) and 500 µmol l^–1 of the phosphodiesterase inhibitor IBMX (D). These experiments show that increases in intracellular cAMP concentration mimic the acidifying effect of 5-HT stimuli. (E) Quantitative analysis of the experiments. Data are means ± s.e.m.; the number of experiments is given in parentheses.