. Multimodal assessment of pain in the esophagus: a new experimental model. Am

Visceral hyperalgesia/allodynia can be induced experimentally and assessed quantitatively by the newly introduced multi-modal psychophysical assessment approach. The significant changes of the experimentally evoked referred pain patterns and of the nociceptive reflex evoked from a distant somatic structure indicate that even short-lasting visceral hyperalgesia can generate generalised sensitisation.

The interaction between visceral pain and the sympathetic nervous system is only sparsely investigated in quantitative human studies. Referred visceral pain can be evoked experimentally by application of substances such as capsaicin (the pungent substance of chilli pepper) to the gut. The aim of the present study was to induce referred visceral pain from the small and large intestine in 32 volunteers via the stomal opening in patients with ileo- or colostomy and quantify the viscero-somatic reflex responses in these referred pain areas by thermography and laser doppler flowmetry. Capsaicin evoked pain and referred pain areas in all subjects. In the referred pain area, the temperature increased by approximately 0.6 degrees C (P<0.001) and the blood flow by approximately 35AU (P<0.001). Saline was used in a control experiment, and no temperature and blood flow changes were found. The present quantitative human study of viscero-somatic reflexes showed dramatic sympathetic responses in the referred pain areas after experimentally induced gut pain.

Generalized hypoalgesia to experimental visceral and somatic stimulations was found in chronic pancreatitis. The findings suggest that the activation and modulation of central mechanisms is fundamental in pancreatic pain, and future studies should address the effect of analgesics with central effects in the treatment of these patients.