We characterized cortical microvascular PO2 and blood flow changes in response to whisker stimulation in awake mice. The measurements were performed by combining two-photon microscopy imaging of the cortical oxygenation and optical coherence tomography imaging of the cerebral blood flow. In order to perform fast spatio-temporally resolved measurements of PO2, we used a newly-developed oxygen-sensitive probe PtG-2P, which has significantly higher brightness than the established two-photon-enhanced oxygen sensor PtP-C343. We characterized the performance of the new probe in vivo and mapped the amplitudes and shapes (e.g. initial dip, overshoot, and post stimulus undershoot) of the PO2 changes as a function of the vessel type (e.g., arterioles, capillaries, and venules) and a distance from the activation center. The measurements in the awake mice are not affected by the confounding factors of anesthesia on the animal physiology, including the level of cerebral metabolism and the amplitude and speed of neuronal and vascular responses. Our results will help to understand changes in oxygenation and blood flow on the cortical microvascular scale, will lead to improved understanding of the cerebral physiology, pathophysiology and will improve quantitative interpretation of fMRI signals.
Ikbal Sencan, Tatiana V. Esipova, Kivilcim Kilic, Baoqiang Li, Michèle Desjardins, Mohammad A. Yaseen, Hui Wang, Rajeshwer S. Jaswal, Sreekanth Kura, Buyin Fu, David A. Boas, Anna Devor, Sava Sakadžić, and Sergei A. Vinogradov, "Measurement of cortical functional activation in awake mice using two-photon microscopy and a novel pO2-sensitive probe (Conference Presentation)," Proc. SPIE 10051, Neural Imaging and Sensing, 100510S (Presented at SPIE BiOS: January 31, 2017; Published: 19 April 2017); https://doi.org/10.1117/12.2255035.5371358603001.
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