Figure 8. Brief elevation of [Ca²⁺]_i to high levels does not evoke WPb exocytosis.

A, a continuous record of [Ca²⁺]_i (i) and C_m (ii) from a cell that had been 72 h in culture, voltage clamped at -50 mV and dialysed with a solution containing 500 μm furaptra and calcium-DM-nitrophen (2.4:4 mm). A single, brief (1 ms) pulse of near-UV light (1500 μF, 200 V) was applied at the time indicated by the vertical dashed lines on the records in A(ii) and (iii) and B(i) and (ii). The detected C_m steps (exocytotic represented by upward lines, and endocytotic by downward lines) are shown in (iii). The area between the stars was excluded from step analysis due to a series of large I_m fluctuations that might have produced spurious changes in C_m. B, the early part of the [Ca²⁺]_i (i) and C_m (ii) response on an expanded time scale. The p-p noise was 0.88 ± 0.30 fF for the period shown. †, the point at which a C_T and R_s compensation was applied.