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How should we define a nociceptor in the gut-brain axis?
Nick J Spencer1, Tim Hibberd1, Zili Xie2
1Visceral Neurophysiology Laboratory, College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University, Bedford Park, SA, Australia.
Frontiers in Neuroscience
|January 5, 2023
Summary
Gut-brain communication relies on spinal afferents, but their nerve endings are poorly understood. Most gut afferent nerve endings express TRPV1 and activate at low thresholds, challenging the definition of gut nociceptors.
Area of Science:
- Neuroscience
- Gastroenterology
- Sensory Biology
Background:
- Emerging data highlight the gut-brain axis in health and disease.
- Sensory nerve endings in the skin are well-characterized, unlike those in visceral organs.
- Spinal afferents are crucial for gut-to-brain sensory pathways.
Purpose of the Study:
- To characterize the morphology and function of spinal afferent nerve endings in the gut.
- To investigate the role of TRPV1 in gut sensory neurons.
- To redefine nociception in the context of visceral pain.
Main Methods:
- Histological analysis of spinal afferent nerve endings in the gut.
- Electrophysiological recordings to assess neuronal activation thresholds.
- Immunohistochemistry to identify specific ion channels like TRPV1.
Main Results:
- Spinal afferent nerve endings in the gut have only recently been identified.
- The majority of these nerve endings express the ion channel TRPV1.
- Many TRPV1-expressing neurons activate at physiological, non-painful levels.
Conclusions:
- The definition of a gut nociceptor is complex due to TRPV1 expression and low activation thresholds.
- Gut nociception may involve diverse spinal afferent nerve ending morphologies, not just free endings.
- Further research is needed to understand visceral pain mechanisms.
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