Figure 1.

Extrinsic afferents in the spinal innervation of mouse colon and rectum (colorectum). A) The lumbar splanchnic (LSN) and pelvic nerves (PN) dominate the innervation of the colonic and rectal regions, respectively. B) Afferent endings are differentially distributed in the colorectum between the LSN and PN innervations. Notice that proximal colonic regions out of the mesenteric zone have no spinal afferent innervations. C) Three mechanical stimuli are applied to the afferent receptive fields in the colorectum to evoke responses revealed by single-unit electrophysiological recordings. D) Colorectal afferents are categorized into 5 classes based on their response profiles to the three mechanical stimuli. Mesenteric afferents have endings not in the colorectum but in the mesentery. MPG: major pelvic ganglion; IMG: inferior mesenteric ganglion; c.stretch: circumferential stretch; HTh.prob: high-threshold probing;