Figure 6.

Duration of application of a small concentration of agonist shapes recovery of response to ATP of DRG neurons. (a) Example of protocol to test low concentration of agonist (100 nM α,β-meATP) on ATP responses. Conditioning agent, which does not induce any measurable membrane current, is switched off immediately before applying ATP and yet it fully desensitizes the subsequent test₁ response. Test₂ response is generated at a fixed 1.5 min interval after test₁ to probe recovery from desensitization. (b) Length of conditioning application of 100 nM ATP (open circles) or 100 nM α,β-meATP (filled circles) versus amplitude of test₂ responses evoked by 10 μM ATP. Note that the amplitude of test₂ responses is uniformly depressed by ATP conditioning (n=5–7 cells). Conversely, conditioning with 100 nM α,β-meATP largely facilitates recovery of test₂ responses, a phenomenon dependent on the length of α,β-meATP conditioning (n=4–6 cells).