Electrophysiological characterization of vagal afferents relevant to mucosal nociception in the rat upper oesophagus

Publikation: Beitrag in FachzeitschriftForschungsartikelBeigetragenBegutachtung

Beitragende

Abstract

Emerging evidence indicates a nociceptive role of vagal afferents. A distinct oesophageal innervation in the rat, with muscular and mucosal afferents travelling predominantly in the recurrent (RLN) and superior laryngeal nerve (SLN), respectively, enabled characterization of mucosal afferents with nociceptive properties, using novel isolated oesophagus-nerve preparations. SLN and RLN single-fibre recordings identified 55 and 14 units, respectively, with none conducting faster than 8.7 m s(-1). Mucosal response characteristics in the SLN distinguished mechanosensors (n = 13), mechanosensors with heat sensitivity (18) from those with cold sensitivity (19) and a mechanoinsensitive group (5). The mechanosensitive fibres, all slowly adapting, showed a unimodal distribution of mechanical thresholds (1.4-128 mN, peak similar to 5.7 mN). No difference in response characteristics of C and A delta fibres was encountered. Mucosal proton stimulation (pH 5.4 for 3 min), mimicking gastro-oesophageal reflux disease (GORD), revealed in 31% of units a desensitizing response that peaked around 20 s and faded within 60 s. Cold stimulation (15 degrees C) was proportionally encoded but the response showed slow adaptation. In contrast, the noxious heat (48 degrees C) response showed no obvious adaptation with discharge rates reflecting the temperature's time course. Polymodal (69%) mucosal units, > 30% proton sensitive, were found in each fibre category and were considered nociceptors; they are tentatively attributed to vagal nerve endings type I, IV and V, previously morphologically described. All receptive fields were mapped and the distribution indicates that the posterior upper oesophagus may serve as a 'cutbank', detecting noxious matters, ingested or regurgitated, and triggering nocifensive reflexes such as bronchoconstriction in GORD.

Details

OriginalspracheEnglisch
Seiten (von - bis)229-242
Seitenumfang14
FachzeitschriftJournal of Physiology
Jahrgang582
Ausgabenummer1
PublikationsstatusVeröffentlicht - 1 Juli 2007
Peer-Review-StatusJa

Externe IDs

PubMed 17478536
Scopus 34347253593
ORCID /0000-0001-9713-0183/work/146645676

Schlagworte

Schlagwörter

  • Superior laryngeal nerve, Dorsal-root ganglia, Sensing ion-channel, Guinea-pig, Gastroesophageal-reflux, Spinal-cord, Vegetative innervation, Sympathetic afferents, Calcitonin-gene, Visceral pain

Bibliotheksschlagworte