Figure 6.

Depletion of SR Ca²⁺ stores but not 5-HT activates I_NSC. (a) 5-HT (10 μM) and ionomycin (1 μM) effects on fura-2 quench by Mn²⁺. (b) Lack of effect of 10 μM 5-HT on membrane currents in PASMC. (c) Intracellular Ca²⁺ store-depletion-induced nonselective cation currents in the absence and presence of 10 mM Ni²⁺. (d) Representative currents in response to a 180 ms voltage ramp from −100 to +100 mV from a single PASMC before (dashed line) and after (gray line) store depletion. I_SOC current amplitude (black line) obtained by subtracting currents before store depletion from currents following store depletion. Cells were held at 0 mV and stepped every 15 s to −60 mV for 200 ms in (b, c). (e) Simultaneous depletion of InsP₃ and caffeine–ryanodine-sensitive intracellular Ca²⁺ stores is required to activate I_SOC. Bars show the mean current density measured at a potential of −60 mV before (open bars) and after releasing or depleting the intracellular Ca²⁺ stores (black). See text for experimental details. Error bars represent±s.e.m. Agonists were present at times shown by the bars. ^*Means significantly different from their controls by a two-tailed paired t-test test (P<0.05).