Figure 3.

Role of calcium and calcium permeable channels in 5-HT-induced ${{\text{O}}_2}^{\underset{\_}{•}}$ increase in rat IPA. (A) Effect of removal of Ca²⁺ from the sarcoplasmic reticulum (${\text{Ca}}_{\text{i}}^{2+}$, dark gray column) or extracellular Ca²⁺ (${\text{Ca}}_{\text{e}}^{2+}$, light gray column), or both ${\text{Ca}}_{\text{i}}^{2+}$and ${\text{Ca}}_{\text{e}}^{2+}$ (hatched column) on ${{\text{O}}_2}^{\underset{\_}{•}}$ produced by 100 μM 5-HT and measured by EPR spectrometry. Effect of nicardipine (1 μM), an L-type voltage-gated calcium channel inhibitor (dark gray column) or two antagonists of voltage-independent calcium permeable channel, RHC-80267 (50 μM) and LOE-908 (10 μM) (dark and light gray columns respectively) on the ${{\text{O}}_2}^{\underset{\_}{•}}$ produced by 100 μM 5-HT (B and C respectively). Data are expressed as mean ± SEM. ^** and ^* mean a significant difference for P < 0.01 and P < 0.05 respectively. n is the number of rats.