Figure 4.

Measurement of fractional Ca²⁺ currents (P_f) through TRP and TRPL channels. (A) Mean P_f values (mean ± SE) are plotted as a function of intensity for TRP channels (isolated in trpl, n = 6), TRPL channels (isolated in trp, n = 8), native TRP+TRPL channels (in WT, n = 20), and TRP+TRPL channels (in dSK⁻, n = 12). Empirical P_f data were obtained from the charge integral ratio between the total LIC and the exchanger tail current (see Materials and Methods), and compared with P_f predictions using the GHK equation (horizontal lines). (B) Responses to 5 ms flashes containing 17,500 photons (arrow) in the trpl photoreceptor were unaffected in the presence of 10 μM thapsigargin for >2–3 min (gray trace) compared with control exposed to vehicle (0.1% DMSO; black trace). The bar graph shows that P_f values in the presence of thapsigargin were indistinguishable from controls (n =3).