T1462 Central Sensitization - Induction of Both Rectal Hypersensitivity and Activation of the Diffuse Noxious Ihibitory Control (DNIC) Following Acid and Capsaicin Infusion in the Human Esophagus

Abstract

INTRODUCTION: As visceral afferents from different regions of the gastrointestinal tract converge at the level of the spinal cord, we hypothesized that strong sensitization of oesophagus could induce widespread visceral hypersensitivity and DNIC activation at the same time. METHODS: Fifteen healthy volunteers (11 males, mean age 33, range 24-52 years) underwent randomized investigation two different days. Moderate pain assessment was measured at baseline and 30, 60 and 90 minutes after an experimental esophageal perfusion with either placebo or 180 ml 0.1M HCl + 2 mg capsaicin. An esophageal catheter was designed for electrical stimulation and perfusion. A multimodal rectal probe including electrical, mechanical and heat stimulation was developed to evaluate remote viscero-visceral hyperalgesia to the esophageal sensitization. Referred pain areas were drawn to all modalities. RESULTS: An increased sensitivity to mechanical (P=0.01) and heat stimulation (P<0.01) was demonstrated in the rectum. Simultaneously a decreased sensitivity to electrical stimulation was found both in the esophagus (P<0.03) lasting all 90 minutes and in the sigmoid colon (P<0.001) at 60 minutes after sensitization. Referred pain areas during heat and mechanical stimulation were unchanged. Referred pain areas to electrical stimulation were reduced in esophagus in the treated group (P=0.01) and increased in sigmoid colon in the treated group (P=0.03). CONCLUSION: This study provides new evidence of central sensitization. The model mimics clinical pain such as patients suffering from IBS or other functional gastrointestinal diseases. The activation of DNIC (either modality specific or through spinal or supraspinal pathways) could make this model suitable for future pharmacological studies of drug intervention.