MicroPET detection of regional brain activation induced by colonic distention in a rat model of visceral hypersensitivity

J Vet Med Sci. 2008 Jan;70(1):43-9. doi: 10.1292/jvms.70.43.


Using microPET and (18)F-fluorodeoxyglucose ((18)F-FDG) as a tracer, we investigated regional brain activation in a rat model of visceral hypersensitivity induced by 2,4,6-trinitrobenzene sulfonic acid (TNBS). TNBS injection into the proximal colon through laparotomy resulted in a significant, sustained decrease in the pain threshold to mechanical distention of the distal colon, indicating a phenomenon referred to as visceral hypersensitivity. When TNBS-induced colonic hypersensitivity was fully developed, all the TNBS-treated rats presented characteristic pain behaviors in response to colonic distention at previously innocuous pressure (0-35 mmHg) that produced no abdominal pain in sham-operated control animals. In microPET study, colonic distention at the normally non-painful pressure produced significant increases in (18)F-FDG uptake in the thalamus and sensory cortex I of TNBS-treated rats. Since the increases in (18)F-FDG uptake in the brain regions were completely abolished by an analgesic dose of morphine (375 microg/kg, s.c.), it is most likely that the regional brain activation detected by microPET is a pain-related central event. The pharmacological and microPET data indicate that colonic distention at the normally non-painful pressure activates specific brain regions in rats with TNBS-induced visceral hypersensitivity, and the microPET protocol described here could provide an objective measure to test visceral analgesic compounds.

MeSH terms

  • Animals
  • Brain / metabolism*
  • Colon / drug effects*
  • Colon / physiology*
  • Fluorodeoxyglucose F18 / pharmacology
  • Male
  • Models, Animal
  • Morphine / pharmacology
  • Pain / metabolism*
  • Positron-Emission Tomography / methods*
  • Radiopharmaceuticals / pharmacology
  • Rats
  • Rats, Sprague-Dawley
  • Trinitrobenzenesulfonic Acid / pharmacology


  • Radiopharmaceuticals
  • Fluorodeoxyglucose F18
  • Morphine
  • Trinitrobenzenesulfonic Acid