Figure 5.

Voltage-evoked [Ca²⁺]_i rise is sensitive to extracellular Ca²⁺ channel blockers. A, [Ca²⁺]_i increases (trace below) and clamp current (trace above) during 20-s steps from −50 to −200 mV (⊔, above) before and after adding 0.1 mm GdCl₃ to the bath. Period of GdCl₃ exposure is indicated by the open bar. Data are from one guard cell in 5 mm Ca²⁺-Mes, pH 6.1, with 10 mm KCl. Inset, Clamp current during steps to −200 mV (⊔, above) replotted on expanded time scale shows characteristic activation of the I_K,in current (Grabov and Blatt, 1997) when the [Ca²⁺]_i rise is suppressed in the presence of Gd³⁺ (fine line) and its time-dependent inactivation when [Ca²⁺]_i rises in the absence of Gd³⁺ (solid line). B, [Ca²⁺]_i increases evoked during 20-s steps from −50 to −200 mV (⊔, above) before and after adding 0.5 μm calcicludine to the bath. Data are from one guard cell in 5 mm Ca²⁺-Mes, pH 6.1, with 10 mm KCl. Period of exposure to the Ca²⁺ channel blocker is indicated by an open bar. Time scale (below), 2 min.