Fig. 6.

Effect of 2-APB on (A) muscarinic cationic current (mI_cat), (B) CCh-induced membrane depolarization and (C) CCh-induced [Ca²⁺]_i mobilization. (A) mI_cat was activated at −50 mV by 10 μM CCh in SMC with [Ca²⁺]_i clamped at 100 nM with Ca²⁺/BAPTA buffer and was recorded in Cs⁺-containing solutions (see Section 2). Peak mI_cat (a) triggered by the second CCh application (Test) was related to that triggered by the first CCh application (Control). 30 μM 2-APB reduced the peak mI_cat (b) on average (n = 6) by 61.5% (c). The symbol (*) shows the significant difference (p < 0.0002) between control and 2-APB. Application of 10 μM CCh depolarized the cell membrane from −33 ± 2 mV to −4 ± 1 mV in control (Ba) and from −29 ± 4 mV to −5 ± 1 mV (n = 5) in 30 μM 2-APB (Bb). Summarized in (Bc). The fluo-4-loaded SMC was stimulated with 600-ms pulses of 10 μM CCh at 10-min intervals and imaged at 39 Hz (C). The time course of the normalized fluo-4 fluorescence averaged within nine sub-PM regions (outlined) was plotted in control (a), after incubation with 30 μM 2-APB (b) and after incubation with 5 μM nicardipine in the presence of 30 μM 2-APB (c). The galleries below the plot show sequential images (after rotation by 90°) taken during the period highlighted in the plot.