Functional MRI of somatosensory activation in rat: Effect of hypercapnic tip-regulation on perfusion- and BOLD-imaging

✍ Scribed by Christian Bock; Bernd Schmitz; Christian M. Kerskens; Michael L. Gyngell; Konstantin-Alexander Hossmann; Dr. Mathias Hoehn-Berlage

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 617 KB
• Volume: 39
• Category: Article
• ISSN: 0740-3194
• DOI: 10.1002/mrm.1910390316

✦ Synopsis

Abstract

Functional activation of somatosensory cortex was studied in α‐chloralose anesthetized rats by functional magnetic resonance imaging (fMRI), using both perfusion–weighted and T~2~*–weighted (blood oxygenation level dependent, BOLD) imaging. The sensitivity of functional activation was altered by ventilating animals for 3 minutes with 6% CO~2~. Before hyper–capnic conditioning, electrical stimulation of the left forepaw at a frequency of 3 Hz led to an increase of signal intensity (relative to the unstimulated baseline condition) in the right somatosensory cortex by 6 ± 2% (means ± SD) in T~2~*–weighted images and by 45% ± 48% in perfusion–weighted images. After hypercapnic conditioning the signal intensity increase in perfusion–weighted images doubled to 91% ± 62% (P = 0.034), whereas that of T~2~*–weighted images only marginally increased to 7 ± 4% (not significant). This different behavior in both imaging modalities is interpreted as evidence for an increased flow response in combination with a higher oxygen extraction. Thus, the fMRI data reflect hypercapniainduced resetting of the functional–metabolic coupling of the tissue during activation.