Perceptual wind-up in the human oesophagus is enhanced by central sensitisation.
BACKGROUND
Oesophageal acid infusion induces enhanced pain hypersensitivity in non-acid exposed upper oesophagus (secondary hyperalgesia) in patients with non-cardiac chest pain, thus suggesting central sensitisation contributes to visceral pain hypersensitivity in functional gut disorders (FGD). Perceptual wind-up (increased pain perception to constant intensity sensory stimuli at frequencies>or=0.3 Hz) is used as a proxy for central sensitisation to investigate pain syndromes where pain hypersensitivity is important (for example, fibromyalgia).


OBJECTIVE
Wind-up in central sensitisation induced human visceral pain hypersensitivity has not been explored. We hypothesised that if wind-up is a proxy for central sensitisation induced human visceral pain hypersensitivity, then oesophageal wind-up should be enhanced by secondary hyperalgesia.


METHODS
In eight healthy volunteers (seven males; mean age 32 years), perception at pain threshold to a train of 20 electrical stimuli applied to the hand and upper oesophagus (UO) at either 0.1 Hz (control) or 2 Hz was determined before and one hour after a 30 minute lower oesophageal acid infusion.


RESULTS
Wind-up occurred only with the 2 Hz train in the UO and hand (both p=0.01). Following acid infusion, pain threshold decreased (17 (4)%; p=0.01) in the UO, suggesting the presence of secondary hyperalgesia. Wind-up to the 2 Hz train increased in the UO (wind-up ratio 1.4 (0.1) to 1.6 (0.1); p=0.03) but not in the hand (wind-up ratio 1.3 (0.1) and 1.3 (0.1); p=0.3)


CONCLUSIONS
Enhanced wind-up after secondary oesophageal hyperalgesia suggests that visceral pain hypersensitivity induced by central sensitisation results from increased central neuronal excitability. Wind-up may offer new opportunities to investigate the contribution of central neuronal changes to symptoms in FGD.
Department of GI Science, Clinical Sciences Building, Hope Hospital, Salford, University of Manchester, M6 8HD, UK. sanchoy@aol.com
S
S
Sarkar
C J
CJ
Woolf
A R
AR
Hobson
D G
DG
Thompson
Q
Q
Aziz
D000328:Adult; D004558:Electric Stimulation; D004947:Esophagus / Q000502:physiology*; D006225:Hand; D006801:Humans; D006851:Hydrochloric Acid / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007858:Learning / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology*; D010469:Perceptual Distortion
D006851:Hydrochloric Acid