Quantitative comparison of colorectal myenteric ganglion density by Full-field optical coherence microscopy (FFOCM) in normal and EdnrB−/− mice. Wild-type (WT; n = 4) and mutant (MUT; n = 5) mice were examined by FFOCM at four different sites in the proximal colon, mid colon, and rectum. Myenteric ganglion density remained consistent along the length of the normal colorectum, while EdnrB−/− colon displayed significant hypoganglionosis, with ganglion density decreasing distally. *P < 0.05, **P < 0.0001.