Figure 4.

A, carbachol (15 μm) activates an inward current across the entire voltage ramp, resulting in a parallel shift of the current–voltage relationship. B, blocking K⁺ conductances with BaCl₂ (1 mm) does not block the effect of carbachol. C–F, the effect of carbachol is instead blocked by replacing 80% of extracellular Na⁺ with choline chloride (low-Na⁺ ACSF; C), is reduced by BAPTA (10 mm in the recording pipette; D) and is blocked by EGTA (10 mm in the recording pipette; E) or by the Na⁺–Ca²⁺ exchanger blocker, KB-R7943 (KB-R; 35 μm; F). All the current–voltage relationships were obtained using voltage ramps (from −100 to −40 mV; 6 mV s⁻¹). G, examples of voltage-clamp recordings (V_h = −60 mV) before and during carbachol applications in BaCl₂ (1 mm), low-Na⁺ ACSF, with BAPTA (10 mm) or EGTA (10 mm) in the recording pipette, and in KB-R7943. H, summary histogram of carbachol-mediated current recorded in control ACSF (con; n = 22; data also represented in Fig. 3H), in BaCl₂ (BaCl₂; n = 6), in low-Na⁺ ACSF (low Na⁺; n = 8), with BAPTA or EGTA in the recording pipette (BAPTA, n = 8; and EGTA, n = 7) and in KB-R7943 (KB-R; n = 12). **P < 0.01, Student's paired t test, comparing holding currents before and during carbachol applications. ††P < 0.01, F_(5,57) = 18.04, P < 0.001, one-way ANOVA, Fisher's PLSD, comparing carbachol-mediated current in control ACSF (con) vs. the carbachol-mediated current of the pharmacologically treated groups (BaCl₂, low Na⁺, BAPTA, EGTA and KB-R). All recordings were conducted in TTX (1 μm).