Assessing CMRO2 during neuronal activation is essential to understanding brain energy metabolism and neurovascular coupling. Over the past decades, preclinical studies have yielded variable results, likely due to differences in techniques, models, and stimulation paradigms. Here, we present the first study using 17O-MRI to directly quantify CMRO2 during paw electrical stimulation in rats at 11.7 T. CMRO2 was significantly higher in the activated cortex (3.28 ± 0.27 µmol/g/min) than in the control cortex (2.89 ± 0.32 µmol/g/min), corresponding to a 13.8% ± 7.9% increase. A strong negative correlation was found between ΔCMRO2 and resting CMRO2, suggesting that baseline oxidative metabolism influences the evoked response. Flow-related parameters (KG, KL, kW) and cerebral blood flow (CBF) were also estimated, revealing a significant 22% increase in CBF in the activated cortex. These findings demonstrate that 17O-MRI is a robust, noninvasive tool for direct CMRO2 quantification during functional activation, with strong potential as a new standard for studying oxidative brain metabolism.
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