Data Shedding Light on Innervation and Visceral Pain

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Questions remain related to the microbiome and how it contributes to sensitization and pain.
Questions remain related to the microbiome and how it contributes to sensitization and pain.

PALM SPRINGS, Calif. — There are several areas of research that remain to be done related to organ innervation and visceral pain, but new data are emerging that are shedding light on the subject and could possibly lead to better treatment, according to a speaker at the American Pain Society Meeting held here.

Gerald Gebhart, PhD, of the University of Pittsburgh, said that much still needs to be learned about sustained afferent organ sensitization –that is, visceral hyperalgesia, and the role the microbiome plays in visceral pain.

“There is a lot of work with respect to the microbiome, but specifically how it contributes to sensitization of gastrointestinal organs remains unknown,” Gebhart said during his plenary lecture.

A main question that needs to be further explored is how anatomically and physiologically the extrinsic and intrinsic innervations of organs interact and contribute to overall visceral pain.

“Those are things that need to be resolved before we gain a better understanding of what's going on with these organs,” Gebhart said. However, he said, data are emerging, particularly in mouse models, that are beginning to shed light on these questions.

Biopsies from the colons of patients with irritable bowel syndrome, for instance, have demonstrated that receptive endings in the colon are sensitized when supernatant is applied.

He said research has focused on targets, including growth factors, chemokines, neuropeptides and others, all of which, he said, have been demonstrated to play a role in experimental sensitization of visceral afferents.

Gebhart cited recently-published mice data by Spencer et al that looked at different types of endings of afferents – using technology that their laboratory developed. 

That group noted four types of receptive endings after examining the filled terminals of colons in mice, specifically, the submucosal and circular muscle, mucosa, longitudinal muscle, and vasculature.

Honing in on targets such as these could presumably, he said, help guide treatments for those patients experiencing chronic visceral pain.

Reference

1. Gebhart G. “Inside Information. Knowns and Unknowns.” Presented at: APS 2015. May 13-16, 2015; Palm Springs, California. 

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