Myenteric neurons in the mouse ileum and colon directly respond to ganglion deformation.

<p>Images of Di-8-ANEPPS stained ileal (<b>A</b>) and colonic (<b>D</b>) myenteric ganglia. <b>B</b> and <b>E</b> show the responses of the myenteric neurons (marked in A and D by white arrows) from ileum and colon, respectively, to intraganglionic volume injection. The lines below all traces mark the onset of the volume injection (steep upward deflection) and the durations of the dynamic (dotted line) and sustained deformations (solid line). The neurons spiked during the dynamic deformation but stopped firing with the beginning of the sustained deformation. Mechanical deformation induced a rapidly adapting spike discharge, typical for rapidly adapting mechanosensitive enteric neurons (RAMEN). <b>C</b> An ileal myenteric neuron responded to two consecutive intraganglionic volume injections with the same spike discharge pattern. <b>F</b> Representative trace illustrating the response of a colonic slowly adapting mechanosensitive enteric neuron (SAMEN) that fired throughout the sustained deformation. <b>G</b> Trace illustrating responses to applying and releasing a force by advancing and retracting the von Frey hair, respectively. In between the von Frey hair was kept in place for 60 s (disrupted line). Note that the discharge pattern is similar and that spikes occur during dynamic force development. Firing frequency of the myenteric RAMEN in the ileum (<b>H</b>) and colon (<b>I</b>). RAMEN fired at significantly higher frequency during the dynamic deformation (ileum: ANOVA on Ranks test; p = 0.009; colon: ANOVA on Ranks test; p = 0.028). Both in the ileum and colon firing frequency of RAMEN did not change after blockade of synaptic transmission by perfusion of low Ca⁺⁺/high Mg⁺⁺ Krebs solution. All signals have been filtered with a Butterworth filter (low pass 180 Hz, high pass 10 Hz).