Figure 6. Effect of MN stimulation on ascending excitatory responses.

A, recordings in an intact tube preparation of ascending responses evoked by transmural stimulation (arrows). Upper traces, circular muscle contractions; lower traces, longitudinal muscle activity. One test cycle is shown, consisting of a control response (Pre-control), a test response (Test) during MN stimulation (dashed line) and a recovery response (Post-control), each separated by 5 min intervals. Note the ‘off’ contraction following the MN stimulation train in each case. B, recordings in a flattened preparation. Responses were evoked by distension of an anally placed balloon (0.08 ml). Upper traces, circular muscle contractions; lower traces, distension. a, control response; b, response during MN stimulation (dashed line); c, response during MN stimulation in the presence of 100 nm idazoxan.