Vagal mechanoreceptors and chemoreceptors in mouse stomach and esophagus

We used a novel in vitro mouse vagus-gastro-esophageal preparation to study the properties of peripheral vagal afferent endings. We found two types of mechanoreceptive fiber, mucosal receptors and tension receptors. These were distinguished by their sensitivity to mucosal stroking with von Frey hairs and circular tension applied via a claw-cantilever system. A comparison was made with gastro-esophageal afferents found in a similar preparation of ferret tissue. Responses of mouse tension receptors to circular tension were significantly greater than ferret tension and tension/mucosal receptors. Similarly the responses of mouse mucosal receptors to mucosal stroking were significantly greater than ferret mucosal and tension/mucosal receptors. Forty-seven percent of mouse mucosal receptors and 50% of tension receptors responded to one or more drugs or chemical stimuli applied to the receptive field. These included alpha,beta-methylene ATP (10(-6) to 10(-3) M), 5-hydroxytryptamine (10(-6) to 10(-3) M), and hydrochloric acid (10(-2) to 10(-1) M). Drug responses were concentration dependent. One hundred percent of mucosal receptors and 61% of tension receptors tested responded to bile (1:8 to 1:1 dilution). A third type of fiber was recruited by bile. These fibers were mechanically insensitive and silent prior to bile exposure. In conclusion, we have shown three types of gastro-esophageal vagal afferent fibers in the mouse: mucosal mechanoreceptors, tension receptors, and specific chemoreceptors activated by bile.