Format

Send to

Choose Destination
J Neurosci. 2018 Jun 20;38(25):5788-5798. doi: 10.1523/JNEUROSCI.0837-18.2018. Epub 2018 May 22.

Optogenetic Activation of Colon Epithelium of the Mouse Produces High-Frequency Bursting in Extrinsic Colon Afferents and Engages Visceromotor Responses.

Author information

1
Department of Pediatrics, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania 15224.
2
Department of Neurobiology, University of Pittsburgh School of Medicine, Center for Pain Research, Center for Neuroscience at the University of Pittsburgh, Pittsburgh, Pennsylvania 15261, and.
3
Department of Neurosciences, University of Toledo, Toledo, Ohio 43614.
4
Department of Neurobiology, University of Pittsburgh School of Medicine, Center for Pain Research, Center for Neuroscience at the University of Pittsburgh, Pittsburgh, Pennsylvania 15261, and bmd1@pitt.edu kaa2@pitt.edu.

Abstract

Epithelial cells of the colon provide a vital interface between the internal environment (lumen of the colon) and colon parenchyma. To examine epithelial-neuronal signaling at this interface, we analyzed mice in which channelrhodopsin (ChR2) was targeted to either TRPV1-positive afferents or to villin-expressing colon epithelial cells. Expression of a ChR2-EYFP fusion protein was directed to either primary sensory neurons or to colon epithelial cells by crossing Ai32 mice with TRPV1-Cre or villin-Cre mice, respectively. An ex vivo preparation of the colon was used for single-fiber analysis of colon sensory afferents of the pelvic nerve. Afferents were characterized using previously described criteria as mucosal, muscular, muscular-mucosal, or serosal and then tested for blue light-induced activation. Light activation of colon epithelial cells produced robust firing of action potentials, similar to that elicited by physiologic stimulation (e.g., circumferential stretch), in 50.5% of colon afferents of mice homozygous for ChR2 expression. Light-induced activity could be reduced or abolished in most fibers using a cocktail of purinergic receptor blockers suggesting ATP release by the epithelium contributed to generation of sensory neuron action potentials. Using electromyographic recording of visceromotor responses we found that light stimulation of the colon epithelium evoked behavioral responses in Vil-ChR2 mice that was similar to that seen with balloon distension of the colon. These ex vivo and in vivo data indicate that light stimulation of colon epithelial cells alone, without added mechanical or chemical stimuli, can directly activate colon afferents and elicit behavioral responses.SIGNIFICANCE STATEMENT Abdominal pain that accompanies inflammatory diseases of the bowel is particularly vexing because it can occur without obvious changes in the structure or inflammatory condition of the colon. Pain reflects abnormal sensory neuron activity that may be controlled in part by release of substances from lining epithelial cells. In support of this mechanism we determined that blue-light stimulation of channelrhodopsin-expressing colon epithelial cells could evoke action potential firing in sensory neurons and produce changes in measures of behavioral sensitivity. Thus, activity of colon epithelial cells alone, without added mechanical or chemical stimuli, is sufficient to activate pain-sensing neurons.

KEYWORDS:

channelrhodopsin; nociceptor; pain; visceral

PMID:
29789376
PMCID:
PMC6010562
[Available on 2018-12-20]
DOI:
10.1523/JNEUROSCI.0837-18.2018

Supplemental Content

Full text links

Icon for HighWire
Loading ...
Support Center