Figure 5.

ASIC subunit composition regulates the effects of big dynorphin. Representative traces (left) and quantification (right) of the effects of big dynorphin on steady-state desensitization of various ASIC subunits expressed in oocytes. Steady-state desensitization was induced in the presence or absence of 100 nm big dynorphin as before with the indicated conditioning pH solutions. Different pH values were used because each channel presented with a distinct pH concentration response of steady-state desensitization. Because different ASIC channels have different pH sensitivities for steady-state desensitization, we used conditioning pH values that were within the linear portion of the steady-state desensitization curve, were an integer of 0.1 pH unit, and reduced acid-evoked current to <50% of maximal current in the absence of peptide. ASIC current was evoked by application of pH 4.5. Peak current amplitude was normalized to maximal ASIC current amplitude in the absence of peptide (I/I _max) (n = 5–12). **p < 0.01 compared with control (Student's t test with paired data). Dyn., Dynorphin.