title: Electrophysiological characterization of human rectal afferents.
abstract: It is presumed that extrinsic afferent nerves link the rectum to the central nervous system. However, the anatomical/functional existence of such nerves has never previously been demonstrated in humans. Therefore, we aimed to identify and make electrophysiological recordings in vitro from extrinsic afferents, comparing human rectum to colon. Sections of normal rectum and colon were procured from anterior resection and right hemicolectomy specimens, respectively. Sections were pinned and extrinsic nerves dissected. Extracellular visceral afferent nerve activity was recorded. Neuronal responses to chemical [capsaicin and "inflammatory soup" (IS)] and mechanical (Von Frey probing) stimuli were recorded and quantified as peak firing rate (range) in 1-s intervals. Twenty-eight separate nerve trunks from eight rectums were studied. Of these, spontaneous multiunit afferent activity was recorded in 24 nerves. Peak firing rates increased significantly following capsaicin [median 6 (range 3-25) spikes/s vs. 2 (1-4), P < 0.001] and IS [median 5 (range 2-18) spikes/s vs. 2 (1-4), P < 0.001]. Mechanosensitive "hot spots" were identified in 16 nerves [median threshold 2.0 g (range 1.4-6.0 g)]. In eight of these, the threshold decreased after IS [1.0 g (0.4-1.4 g)]. By comparison, spontaneous activity was recorded in only 3/30 nerves studied from 10 colons, and only one hot spot (threshold 60 g) was identified. This study confirms the anatomical/functional existence of extrinsic rectal afferent nerves and characterizes their chemo- and mechanosensitivity for the first time in humans. They have different electrophysiological properties to colonic afferents and warrant further investigation in disease states.
authors: Academic Colorectal Unit, Sydney Medical School, Concord, University of Sydney, Sydney, Australia.|Enteric Neuroscience and Gastrointestinal Research Group, ANZAC Research Institute, University of Sydney, Sydney, Australia.
authors: Kheng-Seong
authors: KS
authors: Ng
authors: Discipline of Human Physiology, FMST, School of Medicine, Flinders University, Adelaide, Australia; and.
authors: Simon J
authors: SJ
authors: Brookes
authors: Enteric Neuroscience and Gastrointestinal Research Group, ANZAC Research Institute, University of Sydney, Sydney, Australia.
authors: Noemi A
authors: NA
authors: Montes-Adrian
authors: Department of Integrative Physiology, School of Medicine, Western Sydney University, Sydney, Australia.
authors: David A
authors: DA
authors: Mahns
authors: Academic Colorectal Unit, Sydney Medical School, Concord, University of Sydney, Sydney, Australia; m.a.gladman@sydney.edu.au.|Enteric Neuroscience and Gastrointestinal Research Group, ANZAC Research Institute, University of Sydney, Sydney, Australia.
authors: Marc A
authors: MA
authors: Gladman
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004594:Electrophysiology / Q000295:instrumentation / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009431:Neural Conduction; D012007:Rectum / Q000294:innervation* / Q000502:physiology; D046509:Tissue Culture Techniques / Q000295:instrumentation / Q000379:methods; D017833:Visceral Afferents / Q000502:physiology*
keywords: electrophysiology; human; rectal afferents