Fig 1: 5-HT4 receptor-agonist-induced intracellular cAMP level increases. (A,C,E) Representative traces of transient intracellular cAMP level increases in response to 50 nM BIMU8, with or without 1 µM SQ22536 (A), 5 µM GR113808 (C), or 50 µM GR113808 (E), in the presence of extracellular Ca2+ (2.5 mM) (white boxes at bottom). Black boxes at the top indicate periods of BIMU8 addition to the external solution. White boxes at the top indicate periods of SQ22536 (A) or GR113808 (C,E) addition to the external solution. (B) Bar graphs of BIMU8-induced intracellular cAMP level increases, without (upper column) or with (middle column) 1 µM SQ22536. Recovery (lower column) shows reversible effect of SQ22536. (D) Bar graphs of inhibitory effects of 5 µM GR113808 (middle column) or 50 µM GR113808 (lower column) on the normalized value of 50 nM BIMU8-induced increases in the intracellular cAMP in the presence of GR113808 to that in the absence of GR113808. Each bar in (B,D) denotes the mean ± SE across the number of experiments shown in parenthesis. Statistically significant differences between columns (solid lines) are indicated with asterisks: * p < 0.05.