Fig. 5. PPNDS (pyridoxal-phosphate naphthylazo-nitro-disulfate) also caused avoidance responses (AR) and transient receptor potentials. PPNDS caused 100% AR at approximately 120 µmoll^-1 and the EC₅₀ was approximately 70 µmoll^-1 (A). The transient receptor potential (B) caused by 100 µmoll^-1 PPNDS was similar in amplitude and duration to those seen with 25 µmoll^-1 ß,-methylene ATP (compare with Fig. 2). Two different cells are shown to demonstrate the variability of the responses. The amplitude of the PPNDS receptor potential decreased as a function of time of exposure to 100 µmoll^-1 PPNDS (C). The behavioral bioassays and the recording solution were the same as the solutions used for Figs 1, 2. Each point represents the mean ± S.D. of three trials.