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Updated: Jun 10, 2026
A Protocol for Transcranial Photobiomodulation Therapy in Mice
Published on: November 18, 2018
Targeted increase in cerebral blood flow by transcranial near-infrared laser irradiation
Yoichi Uozumi1, Hiroshi Nawashiro, Shunichi Sato
1Department of Neurosurgery, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359-8513, Japan.
Background And Objective:
Brain function is highly dependent on cerebral blood flow (CBF). The precise mechanisms by which blood flow is controlled by NIR laser irradiation on the central nervous system (CNS) have not been elucidated. In this study, we examined the effect of 808 nm laser diode irradiation on CBF in mice.
Study Design/Materials And Methods:
We examined the effect of NIR irradiation on CBF at three different power densities (0.8, 1.6 and 3.2 W/cm(2)) and directly measured nitric oxide (NO) in brain tissue during NIR laser irradiation using an amperometric NO-selective electrode. We also examined the contribution of NO and a neurotransmitter, glutamate, to the regulation of CBF by using a nitric oxide synthase (NOS) inhibitor, N(g)-nitro-L-arginine methyl ester hydrochloride (L-NAME), and an N-methyl-D-aspartate (NMDA) receptor blocker, MK-801, respectively. We examined the change in brain tissue temperature during NIR laser irradiation. We also investigated the protection effect of NIR laser irradiation on transient cerebral ischemia using transient bilateral common carotid artery occlusion (BCCAO) in mice.
Results:
We showed that NIR laser irradiation (1.6 W/cm(2) for 15-45 minutes) increased local CBF by 30% compared to that in control mice. NIR laser irradiation also induced a significant increase in cerebral NO concentration. In mice that received L-NAME, NIR laser irradiation did not induce any increase in CBF. Mice administered MK-801 showed an immediate increase but did not show a delayed additional increase in local CBF. The increase in brain tissue temperature induced by laser irradiation was estimated to be as low as 0.8 degrees C at 1.6 W/cm(2), indicating that the heating effect is not a main mechanism of the CBF increase in this condition. Pretreatment with NIR laser irradiation improved residual CBF and reduced the numbers of apoptotic cells in the hippocampus.
Conclusion:
Our data suggest that NIR laser irradiation is a promising experimental and therapeutic tool in the field of cerebral circulation research.
Insights
Near-infrared (NIR) laser irradiation significantly increases cerebral blood flow (CBF) in mice by stimulating nitric oxide (NO) production. This finding highlights NIR laser therapy as a potential tool for cerebral circulation research and treatment.
Area of Science:
- Neuroscience
- Biomedical Engineering
- Physiology
Background:
- Cerebral blood flow (CBF) is critical for brain function.
- Mechanisms controlling CBF by near-infrared (NIR) laser irradiation on the central nervous system (CNS) remain unclear.
Purpose of the Study:
- To investigate the effect of 808 nm NIR laser diode irradiation on CBF in mice.
- To elucidate the role of nitric oxide (NO) and glutamate in NIR-induced CBF regulation.
- To assess the neuroprotective effects of NIR laser irradiation during cerebral ischemia.
Main Methods:
- NIR laser irradiation at varying power densities (0.8, 1.6, 3.2 W/cm²).
- Direct measurement of brain tissue nitric oxide (NO) using amperometric electrodes.
- Pharmacological inhibition of nitric oxide synthase (NOS) with L-NAME and NMDA receptor blockade with MK-801.
- Monitoring brain tissue temperature changes.
- Evaluation of NIR laser effects on cerebral ischemia models (transient bilateral common carotid artery occlusion - BCCAO).
Main Results:
- NIR laser irradiation (1.6 W/cm² for 15-45 min) increased local CBF by 30% in mice.
- Cerebral NO concentration significantly increased following NIR irradiation.
- NIR-induced CBF increase was abolished by L-NAME, indicating NO-dependency.
- MK-801 affected immediate but not delayed CBF increase.
- Minimal brain tissue temperature increase (<0.8°C) suggests non-thermal mechanisms.
- NIR laser pretreatment improved residual CBF and reduced hippocampal apoptotic cells during ischemia.
Conclusions:
- NIR laser irradiation effectively increases CBF in mice.
- The mechanism involves nitric oxide (NO) pathway activation.
- NIR laser irradiation demonstrates neuroprotective effects against ischemic injury.
- NIR laser irradiation is a promising tool for cerebral circulation research and potential therapeutic applications.
