Figure 3.

Schematic illustration of the proposed gut layers which are preferentially affected with: (1) Thermal stimuli (mucosa - dark grey and submucosa - light grey); (2) Mechanical stimuli (circular muscle layer - hatched grey and longitudinal muscle layer - prickled grey); (3) Electrical stimuli (all layers depending on stimulus intensity). Perfusion of the esophagus with acid (curved arrows) gives the possibility to evoke peripheral and (mainly) central sensitization (illustrated with stars).