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Cerebral tissue pO2 response to treadmill exercise in awake mice.

ABSTRACT: We exploited two-photon microscopy and Doppler optical coherence tomography to examine the cerebral blood flow and tissue pO2 response to forced treadmill exercise in awake mice. To our knowledge, this is the first study performing both direct measure of brain tissue pO2 during acute forced exercise and underlying microvascular response at capillary and non-capillary levels. We observed that cerebral perfusion and oxygenation are enhanced during running at 5 m/min compared to rest. At faster running speeds (10 and 15 m/min), decreasing trends in arteriolar and capillary flow speed were observed, which could be due to cerebral autoregulation and constriction of arterioles in response to blood pressure increase. However, tissue pO2 was maintained, likely due to an increase in RBC linear density. Higher cerebral oxygenation at exercise levels 5-15 m/min suggests beneficial effects of exercise in situations where oxygen delivery to the brain is compromised, such as in aging, atherosclerosis and Alzheimer Disease.

SUBMITTER: Moeini M

PROVIDER: S-EPMC7414913 | biostudies-literature | 2020 Aug

REPOSITORIES: biostudies-literature

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Cerebral tissue pO2 response to treadmill exercise in awake mice.

Moeini Mohammad M Cloutier-Tremblay Christophe C Lu Xuecong X Kakkar Ashok A Lesage Frédéric F

Scientific reports 20200807 1

We exploited two-photon microscopy and Doppler optical coherence tomography to examine the cerebral blood flow and tissue pO2 response to forced treadmill exercise in awake mice. To our knowledge, this is the first study performing both direct measure of brain tissue pO2 during acute forced exercise and underlying microvascular response at capillary and non-capillary levels. We observed that cerebral perfusion and oxygenation are enhanced during running at 5 m/min compared ...[more]

PMID: 32770089

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Project description:Nitroxide free radicals can serve as redox-sensitive MRI contrast agents useful to image the redox status of tissue of interest. In this study, the effect of oxygen content in the inspired gas on the kinetics of metabolism of three nitroxides has been evaluated in the muscle and tumor in mice. SCC tumors (approximate size of 1.0 cm3) on the right hind leg of female C3H/Hen MTV- mice were prepared. Three nitroxides, 3-carboxy-2,2,5,5-tetramethylpyrrolidine-N-oxyl (CxP), 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-N-oxyl (CmP), and 4-hydroxy-tetramethylpiperidine-N-oxyl (TEMPOL), having different lipophilicities were compared using MR redox imaging. T1-mapping of the tissues was obtained using a multi-slice multi-echo (MSME) sequence with several TRs. The three nitroxides showed differences in accumulation and metabolism/clearance in muscle and tumor. The cell impermeable nitroxide CxP displayed kinetic patterns of slow enhancement followed by a slow decline typical of clearance rather than metabolism. The cell permeable CmP on the other hand showed a relatively faster uptake and metabolism with a modestly higher rate of metabolism in the tumor than muscle. The TEMPOL on the other hand displayed a rapid uptake and reduction with a trend of significantly rapid decay rate in tumor tissue, while slightly higher maximum signal intensity and slower decay rate was observed in normal muscle. The reduction rate of TEMPOL in the tumor was significantly enhanced when the breathing gas had 100%-oxygen while it was not significantly different in the muscle. EPR oximetry studies monitoring the oxygen dependent linewidth of TEMPOL showed that the pO2 in the healthy tissue during carbogen breathing significantly increased normal tissue pO2 compared to air breathing whereas breathing 100%-oxygen made normal tissue slight hypoxic. Since TEMPOL is a radioprotector, our studies show that a combination of 100%-oxygen breathing and TEMPOL has a potential to enhance radioprotective effects to normal tissue.

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Cerebral tissue pO2 response to treadmill exercise in awake mice.

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Cerebral tissue pO<sub>2</sub> response to treadmill exercise in awake mice.

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