RT Journal Article
SR Electronic
T1 Microscopic Quantification of Oxygen Consumption across Cortical Layers
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2021.10.13.464176
DO 10.1101/2021.10.13.464176
A1 Philipp Mächler
A1 Natalie Fomin-Thunemann
A1 Martin Thunemann
A1 Marte Julie Sætra
A1 Michèle Desjardins
A1 Kıvılcım Kılıç
A1 Ikbal Şencan
A1 Baoqiang Li
A1 Payam Saisan
A1 Qun Cheng
A1 Kimberly L. Weldy
A1 David A. Boas
A1 Richard B. Buxton
A1 Gaute T. Einevoll
A1 Anders M. Dale
A1 Sava Sakadžić
A1 Anna Devor
YR 2021
UL http://biorxiv.org/content/early/2021/10/14/2021.10.13.464176.abstract
AB The cerebral cortex is organized in cortical layers that differ in their cellular density, composition, and wiring. Cortical laminar architecture is also readily revealed by staining for cytochrome oxidase – the last enzyme in the respiratory electron transport chain located in the inner mitochondrial membrane. It has been hypothesized that a high-density band of cytochrome oxidase in cortical layer IV reflects higher oxygen consumption under baseline (unstimulated) conditions. Here, we tested the above hypothesis using direct measurements of the partial pressure of O2 (pO2) in cortical tissue by means of 2-photon phosphorescence lifetime microscopy (2PLM). We revisited our previously developed method for extraction of the cerebral metabolic rate of O2 (CMRO2) based on 2-photon pO2 measurements around diving arterioles and applied this method to estimate baseline CMRO2 in awake mice across cortical layers. To our surprise, our results revealed a decrease in baseline CMRO2 from layer I to layer IV. This decrease of CMRO2 with cortical depth was paralleled by an increase in tissue oxygenation. Higher baseline oxygenation and cytochrome density in layer IV may serve as an O2 reserve during surges of neuronal activity or certain metabolically active brain states rather than baseline energy needs. Our study provides the first quantification of microscopically resolved CMRO2 across cortical layers as a step towards informed interpretation and modeling of cortical-layer-specific Blood Oxygen Level Dependent (BOLD) functional Magnetic Resonance Imaging (fMRI) signals.Competing Interest StatementThe authors have declared no competing interest.