BOLD fMRI mapping of brain responses to nociceptive stimuli in rats under ketamine anesthesia

Med Eng Phys. 2008 Oct;30(8):953-8. doi: 10.1016/j.medengphy.2007.12.004. Epub 2008 Feb 20.


Ketamine is one of the most commonly used anesthetics, but its effects on nociceptive responses are not clearly defined. This study used blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to hemodynamically map responses to formalin stimuli under ketamine anesthesia. All imaging was performed on a 4.7-T fMRI system. During dynamic image acquisition, formalin was injected into the rat hindpaw as a painful stimulant. Correlation coefficients were calculated, and each image was registered and fused with the corresponding rat brain atlas so as to avoid inaccuracies arising from manual definition of the brain area and to achieve atlas-based normalization among subjects. Formalin injections were found to increase BOLD signals in the cingulate cortex, sensory-motor cortices, insular cortex, striatum, nucleus accumbens, medial thalamus, ventrolateral thalamic group, and hippocampus. Moreover, in contrast to previous pain investigations, the frontal subcortical regions were strongly activated in ketamine-anesthetized rats.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anesthetics / administration & dosage
  • Animals
  • Brain / drug effects
  • Brain / physiology*
  • Evoked Potentials, Somatosensory / drug effects
  • Evoked Potentials, Somatosensory / physiology*
  • Ketamine / administration & dosage*
  • Magnetic Resonance Imaging / methods*
  • Male
  • Pain Measurement
  • Pain Threshold / drug effects
  • Pain Threshold / physiology*
  • Physical Stimulation / methods
  • Rats
  • Rats, Wistar


  • Anesthetics
  • Ketamine