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Chen BN, Humenick AG, Hibberd TJ, Yew WP, Wattchow DA, Dinning PG, Costa M, Spencer NJ, Brookes SJH. Characterization of viscerofugal neurons in human colon by retrograde tracing and multi-layer immunohistochemistry. Front Neurosci 2024; 17:1313057. [PMID: 38292899 PMCID: PMC10825022 DOI: 10.3389/fnins.2023.1313057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Accepted: 12/15/2023] [Indexed: 02/01/2024] Open
Abstract
Background and Aims Viscerofugal neurons (VFNs) have cell bodies in the myenteric plexus and axons that project to sympathetic prevertebral ganglia. In animals they activate sympathetic motility reflexes and may modulate glucose metabolism and feeding. We used rapid retrograde tracing from colonic nerves to identify VFNs in human colon for the first time, using ex vivo preparations with multi-layer immunohistochemistry. Methods Colonic nerves were identified in isolated preparations of human colon and set up for axonal tracing with biotinamide. After fixation, labeled VFN cell bodies were subjected to multiplexed immunohistochemistry for 12 established nerve cell body markers. Results Biotinamide tracing filled 903 viscerofugal nerve cell bodies (n = 23), most of which (85%) had axons projecting orally before entering colonic nerves. Morphologically, 97% of VFNs were uni-axonal. Of 215 VFNs studied in detail, 89% expressed ChAT, 13% NOS, 13% calbindin, 9% enkephalin, 7% substance P and 0 of 123 VFNs expressed CART. Few VFNs contained calretinin, VIP, 5HT, CGRP, or NPY. VFNs were often surrounded by dense baskets of axonal varicosities, probably reflecting patterns of connectivity; VAChT+ (cholinergic), SP+ and ENK+ varicosities were most abundant around them. Human VFNs were diverse; showing 27 combinations of immunohistochemical markers, 4 morphological types and a wide range of cell body sizes. However, 69% showed chemical coding, axonal projections, soma-dendritic morphology and connectivity similar to enteric excitatory motor neurons. Conclusion Viscerofugal neurons are present in human colon and show very diverse combinations of features. High proportions express ChAT, consistent with cholinergic synaptic outputs onto postganglionic sympathetic neurons in prevertebral ganglia.
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Affiliation(s)
- Bao Nan Chen
- Human Physiology, Medical Bioscience, College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
| | - Adam G. Humenick
- Human Physiology, Medical Bioscience, College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
| | - Timothy James Hibberd
- Human Physiology, Medical Bioscience, College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
| | - Wai Ping Yew
- Human Physiology, Medical Bioscience, College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
| | - David A. Wattchow
- Department of Surgery, Flinders Medical Centre, Bedford Park, SA, Australia
| | - Phil G. Dinning
- Department of Surgery, Flinders Medical Centre, Bedford Park, SA, Australia
| | - Marcello Costa
- Human Physiology, Medical Bioscience, College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
| | - Nick J. Spencer
- Human Physiology, Medical Bioscience, College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
| | - Simon J. H. Brookes
- Human Physiology, Medical Bioscience, College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
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