Functional ¹⁷O-MRI of cerebral oxygen consumption in the activated rat brain

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 (K_G, K_L, k_W) 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.