Gut. 2006 Feb 21; [Epub ahead of print]
Sarkar S, Woolf CJ, Hobson AR, Thompson DG, Aziz Q.
Hope Hospital & University of Manchester, United Kingdom.
BACKGROUND: Oesophageal acid infusion induces enhanced pain hypersensitivity in non-acid exposed upper oesophagus (secondary hyperalgesia) in NCCP patients, thus suggesting central sensitization contributes to visceral pain hypersensitivity in functional gut disorders (FGD). Perceptual wind up (WUP) (increased pain perception to constant intensity sensory stimuli at frequencies>/= 0.3Hz) is used as a proxy for central sensitization to investigate pain syndromes where pain hypersensitivity is important e.g. fibromyalgia.
AIMS: WUP in central sensitization induced human visceral pain hypersensitivity has not been explored. Hypothesis; if WUP is a proxy for central sensitization induced human visceral pain hypersensitivity, then oesophageal WUP should be enhanced by secondary hyperalgesia.
METHODS: In 8 healthy volunteers (7 male; mean age 32 years), perception at pain threshold (PT) to a train of 20 electrical stimuli applied to the hand & the upper oesophagus (UE) at either 0.1Hz (control) or 2Hz was determined before and 1-hour following a 30-minute lower oesophageal acid infusions.
RESULTS: WUP occurred only with the 2Hz train in the UE and hand (Both p=0.01). Following acid infusion, PT decreased (17+4%; p=0.01) in UE, suggesting the presence of secondary hyperalgesia. WUP to the 2Hz train increased in the UE (WUP ratio; 1.4+0.1 to 1.6+0.1; p=0.03) but not the hand (WUP ratio; 1.3+0.1 & 1.3+0.1; p=0.3).
CONCLUSION: The enhanced WUP after secondary oesophageal hyperalgesia suggests that visceral pain hypersensitivity induced by central sensitization, results from increased central neuronal excitability. WUP may offer new opportunities to investigate the contribution of central neuronal changes to symptoms in FGD.
PMID: 16492716 [PubMed – as supplied by publisher]