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The enteroendocrine PYY cell interacts with neurites of the enteric nervous system through axon‐like basal process

PYY‐secreting cells have prominent basal processes of unknown function. We have reported using a PYY‐eGFP mouse model that such processes are up to 50μm long and their ends resemble synapses. Hence, basal processes in PYY‐cells may physically interact with neurites of the enteric nervous system. We performed immunohistochemical staining of colonic sections from PYY‐eGFP mice using neuronal cell markers: calcitonin gene related peptide (CGRP); vasoactive intestinal peptide (VIP); and the axonal proteins neurofilament (NF) 200, NF160, and NF68. Sections were imaged by laser scanning confocal microscopy and 3D reconstructed using Imaris software. VIP‐like immunoreactivity was visible in the pericryptal region but did not appear to contact PYY‐eGFP cells. Neurofilament immunoreactivity was found in the myenteric and submucosal plexuses. Fibers extending from the submucosal plexus into the lamina propria were prominently stained with NF160. Some of these NF160 neurites exhibited CGRP‐immunoreactivity and made direct contact with the PYY‐eGFP basal process. Surprisingly, the basal process in PYY‐eGFP cells also contained the axonal protein NF160. Some, but not all, PYY‐eGFP cell processes were also immunoreactive with NF68. We conclude that the enteroendocrine PYY cell makes physical contact with CGRP‐expressing neurites of the colonic nervous system through an axon‐like basal process.