High-resolution relaxometry-based calibrated fMRI in murine brain: Metabolic differences between awake and anesthetized states. Issue 5 (May 2022)

• Record Type: Journal Article
• Authors: Xu, Mengyang; Bo, Binshi; Pei, Mengchao; Chen, Yuyan; Shu, Christina Y; Qin, Qikai; Hirschler, Lydiane; Warnking, Jan M; Barbier, Emmanuel L; Wei, Zhiliang; Lu, Hanzhang; Herman, Peter; Hyder, Fahmeed; Liu, Zhi-jie; Liang, Zhifeng; Thompson, Garth J
• Is Part Of: Journal of cerebral blood flow & metabolism. Volume 42:Issue 5(2022)
• Page Start: 811
• Page End: 825
• Publication Date: 2022-05
• Subjects: Awake mice -- anesthesia -- dexmedetomidine -- calibrated fMRI -- CMRO2 -- TRUST -- pCASL; Cerebral circulation -- Periodicals; Brain -- Metabolism -- Periodicals; Brain -- Blood-vessels -- Periodicals; Cerebrovascular disease -- Periodicals; 612.824
• DOI: 10.1177/0271678X211062279
• Languages: English
• ISSNs: 0271-678X

Abstract

Functional magnetic resonance imaging (fMRI) techniques using the blood-oxygen level-dependent (BOLD) signal have shown great potential as clinical biomarkers of disease. Thus, using these techniques in preclinical rodent models is an urgent need. Calibrated fMRI is a promising technique that can provide high-resolution mapping of cerebral oxygen metabolism (CMRO2 ). However, calibrated fMRI is difficult to use in rodent models for several reasons: rodents are anesthetized, stimulation-induced changes are small, and gas challenges induce noisy CMRO2 predictions. We used, in mice, a relaxometry-based calibrated fMRI method which uses cerebral blood flow (CBF) and the BOLD-sensitive magnetic relaxation component, R2 ′, the same parameter derived in the deoxyhemoglobin-dilution model of calibrated fMRI. This method does not use any gas challenges, which we tested on mice in both awake and anesthetized states. As anesthesia induces a whole-brain change, our protocol allowed us to overcome the former limitations of rodent studies using calibrated fMRI. We revealed 1.5-2 times higher CMRO2, dependent upon brain region, in the awake state versus the anesthetized state. Our results agree with alternative measurements of whole-brain CMRO2 in the same mice and previous human anesthesia studies. The use of calibrated fMRI in rodents has much potential for preclinical fMRI.