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Light controls cerebral blood flow in naive animals
Ravi L Rungta1, Bruno-Félix Osmanski1, Davide Boido1
1INSERM U1128, Laboratory of Neurophysiology and New Microscopies, Université Paris Descartes, Paris 75006, France.
Nature Communications
|February 1, 2017
Summary
Light stimulation alone, without optogenetics, causes vasodilation in the mouse brain by affecting smooth muscle cells. This finding is crucial for interpreting studies on brain blood flow and neurovascular coupling.
Area of Science:
- Neuroscience
- Physiology
- Biomedical Engineering
Background:
- Optogenetics is a powerful tool for mapping brain activity, often relying on functional hyperaemia (blood flow changes) detected by techniques like opto-functional MRI (opto-fMRI).
- Understanding neurovascular coupling is essential for interpreting brain imaging data and developing therapeutic strategies.
- The direct effects of light stimulation on cerebral blood flow, independent of optogenetic manipulation, require careful evaluation.
Purpose of the Study:
- To investigate whether light stimulation protocols, commonly used in opto-fMRI and neurovascular coupling studies, directly influence blood flow in non-optogenetically modified mouse brains.
- To elucidate the cellular mechanisms underlying light-induced changes in cerebral hemodynamics.
- To assess the energy dependency and reproducibility of observed light-induced vascular responses.
Main Methods:
- Combined two-photon laser scanning microscopy and ultrafast functional ultrasound imaging in naive mice.
- Applied light stimulation protocols similar to those used in opto-fMRI and neurovascular coupling research.
- Monitored neuronal and astrocyte activity alongside arteriolar smooth muscle cell calcium levels and blood flow dynamics.
Main Results:
- In naive mouse brains, light stimulation alone induced a decrease in arteriolar smooth muscle cell calcium, leading to significant vasodilation.
- This light-induced vasodilation occurred independently of neuronal or astrocyte excitation.
- The effect was reversible, reproducible, and energy-dependent, becoming apparent at approximately 0.5 mJ.
Conclusions:
- Light stimulation per se can modulate cerebral blood flow through a direct effect on vascular smooth muscle, independent of optogenetic actuators.
- These findings necessitate careful consideration when interpreting results from optogenetics and neurovascular coupling studies employing light stimulation.
- The controlled, light-induced vasodilation presents a potential avenue for therapeutic interventions aimed at increasing local blood flow.
