EAAC1-immunoreactive neurons are found in the submucosal plexus. A, B, A subset of EAAC1-immunoreactive neurons (A) expresses calbindin immunoreactivity (B, arrow). C, D, EAAC1 immunoreactivity (C) is expressed by all substance P-immunoreactive neurons (D, arrow); however, not all EAAC1-immunoreactive neurons express substance P immunoreactivity (arrowhead). E, F, Confocal photomicrographs (sum of 10 optical sections, collected at 0.5 μm intervals) of a whole mount of the submucosal plexus. EAAC1-immunoreactive nerve fibers encircle intestinal crypts (E, arrow). EAAC1 immunoreactivity is found in a subset of enterochromaffin cells (F). Thearrows indicate prominent staining of the apex of the cells facing the intestinal lumen. Scale bar, 30 μm.