Cerebral tissue pO2 response to treadmill exercise in awake mice

Mohammad Moeini,Christophe Cloutier-Tremblay,Xuecong Lu,Frédéric Lesage,Ashok Kakkar

doi:10.1038/s41598-020-70413-3

Mohammad Moeini, Christophe Cloutier-Tremblay + Show 3 more

Open Access

https://doi.org/10.1038/s41598-020-70413-3

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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.

Highlights

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
Exercise-induced changes in several parameters that contribute to cerebral tissue oxygenation [such as the heat rate, cardiac output, blood pressure, blood pO2 and p CO2, CMRO2 and cerebral blood flow (CBF)] have been well characterized before[1,4,5,14,15,16,17,18,19,20]
There are a number of near-infrared spectroscopy (NIRS) studies that investigated the oxygen saturation of hemoglobin in the brain during exercise[1,5,7,15,21], but again the interpretation of tissue oxygenation from these data is not straightforward, because cerebral tissue pO2 is affected by other factors, such as CBF and CMRO2, which are modulated by exercise

Summary

Introduction

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. Blood flow speed in larger vessels was quantified using Doppler optical coherence tomography (Doppler OCT) to investigate how changes in capillary flow are mediated To our knowledge, this is the first study investigating the relationship between the cerebral tissue pO2 (direct measure), exercise intensity and the underlying microvascular response involved

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