Fig. 7.

Ca²⁺ dependence of I_Cl(Ca) in rods and cones. The amplitudes of inward Cl(Ca) currents evoked by flash photolysis of caged Ca²⁺ were plotted as a function of intraterminal [Ca²⁺]. Data were fit with sigmoidal concentration–response curves (see methods). The best fit for data from rods (A) was obtained with a half-maximal effective concentration (EC₅₀) of 556 nM and slope factor of 1.76 (n = 88). The best fit for data from cones (B) was obtained with an EC₅₀ of 377 nM and slope factor of 2.44 (n = 34). Repeated measurements in an individual rod (C) and cone (D) yielded a similar sigmoidal relationship. For these 2 cells, the best fits were obtained with EC₅₀ values of 675 and 262 nM and slope factors of 2.56 and 2.44, respectively.