Fig. 1.

Depolarisation and carbachol-evoked increases in [Ca²⁺]_c. (A,B) Depolarisation (−70 mV to +10 mV; Ae) activated a voltage-dependent Ca²⁺ current (Ad) to cause an increase in [Ca²⁺]_c (Aa,Ab) that occurred at the same time throughout the cell. In contrast, carbachol (CCh; Bc) evoked an increase in [Ca²⁺]_c that began in one region (region i) and propagated away from that site (Ba,Bb). The [Ca²⁺]_c images (Aa,Ba) are derived from the time points indicated by the corresponding numbers in Aa and Ba. [Ca²⁺]_c changes in Aa and Ba are represented by colour; blue is low and red is high [Ca²⁺]_c. Changes in the fluorescence ratio with time (Ab,Bb) are derived from 3×3 pixel boxes from the second panel in Aa; regions i to v are drawn as larger yellow circles to facilitate visualisation. A brightfield image of the cell is shown (Aa; left panel); the whole-cell patch electrode is on the left side. The carbachol-containing puffer pipette is located to the right of the cell outside the field of view. The inward current evoked during carbachol application (Bd) might arise from activation of Ca²⁺-activated Cl⁻ channels or non-specific cation channels (Inoue and Isenberg, 1990; Lee et al., 1993), and was not studied further here.