Imaging oxygen consumption in forepaw somatosensory stimulation in rats under isoflurane anesthesia

Zhaohui M. Liu, Karl F. Schmidt, Kenneth M. Sicard, Timothy Q. Duong

Research output: Contribution to journalArticlepeer-review

125 Scopus citations


The cerebral metabolic rate of oxygen (CMRO2) was dynamically evaluated on a pixel-by-pixel basis in isoflurane-anesthetized and spontaneously breathing rats following graded electrical somatosensory forepaw stimulations (4, 6, and 8mA). In contrast to α-chloralose, which is the most widely used anesthetic in forepaw-stimulation fMRI studies of rats under mechanical ventilation, isoflurane (1.1-1.2%) provided a stable anesthesia level over a prolonged period, without the need to adjust the ventilation volume/rate or sample blood gases. Combined cerebral blood flow signals (CBF) and blood oxygenation level-dependent (BOLD) fMRI signals were simultaneously measured with the use of a multislice continuous arterial spin labeling (CASL) technique (two-coil setup). CMRO2 was calculated using the biophysical BOLD model of Ogawa et al. (Proc Natl Acad Sci USA 1992;89:5951-5955). The stimulus-evoked BOLD percent changes at 4, 6, and 8mA were, respectively, 0.5% ± 0.2%, 1.4% ± 0.3%, and 2.0% ± 0.3% (mean ± SD, N = 6). The CBF percent changes were 23% ± 6%, 58% ± 9%, and 87% ± 14%. The CMRO2 percent changes were 14% ± 4%, 24% ± 6%, and 43% ± 11%. BOLD, CBF, and CMRO2 activations were localized to the forepaw somatosensory cortices without evidence of plateau for oxygen consumption, indicative of partial coupling of CBF and CMRO 2. This study describes a useful forepaw-stimulation model for fMRI, and demonstrate that CMRO2 changes can be dynamically imaged on a pixel-by-pixel basis in a single setting with high spatiotemporal resolution.

Original languageEnglish (US)
Pages (from-to)277-285
Number of pages9
JournalMagnetic Resonance in Medicine
Issue number2
StatePublished - Aug 2004
Externally publishedYes


  • Arterial spin labeling
  • BOLD
  • CBF
  • CMR
  • Cerebral metabolic rate of oxygen
  • Lactate
  • Oxidative metabolism
  • Perfusion
  • fMRI

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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