Fig. 6.

The effects on transducer adaptation of a low-affinity Ca²⁺ buffer, nitro-BAPTA, compared with BAPTA. A, Families of transducer currents recorded with 1 mm BAPTA or with 0.9 mm nitro-BAPTA plus 0.1 mm BAPTA in 0.07 mm external Ca²⁺. Note that although adaptation is slow under both conditions, a larger fraction of current is turned on at rest with the 1 mm BAPTA. B, Collected measurements of the fraction of total current activated at rest,P_O (rest), and the time constant of adaptation, τ_ad, as a function of the external Ca²⁺ concentration for recordings with BAPTA (open symbols, continuous lines) and 0.9 mm nitro-BAPTA plus 0.1 mm BAPTA (filled symbols, dashed lines; 6 cells). Note that nitro-BAPTA is equivalent to a 10-fold smaller BAPTA concentration in affecting the fraction of current activated at rest but is at least as effective as BAPTA in altering the adaptation time constant. Measurements on six cells are included for nitro-BAPTA. Error bars for BAPTA results are shown in Figure 3.