Fig. 1. Enteroendocrine cells contact sensory nerve fibers.

(A) CckGFP_Pgp9.5GFP mice express GFP in CCK-enteroendocrine cells and Pgp9.5 sensory nerve fibers. The two cell types are shown in the enlarged view, with the CCK- enteroendocrine cell represented by a triangle. (B) Confocal microscopy image of proximal small intestine villus showing a GFP-labeled CCK-enteroendocrine cell and GFP-labeled Pgp9.5 nerve fibers; 18.9 ± 2.0% SEM of CckGFP cells contact Pgp9.5 fibers (n = 3 mice, >100 cells per mouse). (C) PYY-stained enteroendocrine cells (left, green) in the colon contact Phox2b vagal nerve fibers (center, red) in a Phox2bCRE_tdTomato mouse; merged image is shown on the right. (D) Two-thirds of CckGFP (green) enteroendocrine cells colocalize with the presynaptic marker synapsin-1 (purple) (n = 6 mice, 200 cells per mouse). (E) Real-time quantitative polymerase chain reaction (qPCR) expression levels of presynaptic transcripts, including genes encoding for synaptic adhesion proteins (n = 3 mice, >10,000 cells per cell type per mouse; error bars indicate mean ± SEM; a.u., arbitrary units; EEC, enteroendocrine cell). All scale bars, 10 μm.