Fig. 5.

ATP can desensitize the train of APs evoked by ATP. A–D, Representative voltage traces from a single AH neuron; the dotted lines indicate RMP. Calibration in B applies to all traces. ATP was applied twice to the mucosa at the vertical lines with a 2, 4, 6, or 8 sec interval (A–D, respectively); the total number of APs is shown to theright of each trace. The diagonal lines indicate a break in the trace of a variable length of time. In control (A–D), ATP evokes a burst of APs consisting of between seven and nine APs. Subsequent APs evoked by the second application of ATP are depressed when the interval is shorter than 8 sec. Note that the long AHP after AP generation does not prevent incoming APs from the distal processes from evoking PPPs.E–G, Calibration in G also applies to E. The total number of ATP-evoked APs is shown to the right of each trace.E, In control, ATP evoked a burst of APs consisting of between seven and nine APs (3 repetitions). F, α,β-me-ATP was then applied six times in rapid succession to the same region of mucosa, and ATP was applied immediately after.G, Two minutes later, the ATP response was fully recovered.