A Protocol for Transcranial Photobiomodulation Therapy in Mice

Summary

Photobiomodulation therapy is an innovative noninvasive modality for the treatment of a wide range of neurological and psychiatric disorders and can also improve healthy brain function. This protocol includes a step-by-step guide to performing brain photobiomodulation in mice by transcranial light delivery, which can be adapted for use in other laboratory rodents.

Abstract

Transcranial photobiomodulation is a potential innovative noninvasive therapeutic approach for improving brain bioenergetics, brain function in a wide range of neurological and psychiatric disorders, and memory enhancement in age-related cognitive decline and neurodegenerative diseases. We describe a laboratory protocol for transcranial photobiomodulation therapy (PBMT) in mice. Aged BALB/c mice (18 months old) are treated with a 660 nm laser transcranially, once daily for 2 weeks. Laser transmittance data shows that approximately 1% of the incident red light on the scalp reaches a 1 mm depth from the cortical surface, penetrating the dorsal hippocampus. Treatment outcomes are assessed by two methods: a Barnes maze test, which is a hippocampus-dependent spatial learning and memory task evaluation, and measuring hippocampal ATP levels, which is used as a bioenergetics index. The results from the Barnes task show an enhancement of the spatial memory in laser-treated aged mice when compared with age-matched controls. Biochemical analysis after laser treatment indicates increased hippocampal ATP levels. We postulate that the enhancement of memory performance is potentially due to an improvement in hippocampal energy metabolism induced by the red laser treatment. The observations in mice could be extended to other animal models since this protocol could potentially be adapted to other species frequently used in translational neuroscience, such as rabbit, cat, dog, or monkey. Transcranial photobiomodulation is a safe and cost-effective modality which may be a promising therapeutic approach in age-related cognitive impairment.

Introduction

PBMT, or low-level laser light therapy (LLLT), is a general term which refers to therapeutic methods based on the stimulation of biological tissues by light energy from lasers or light-emitting diodes (LEDs). Almost all PBMT treatments are applied with red to near-infrared (NIR) light at wavelengths from 600 to 1100 nm, an output power ranging from 1 to 500 mW, and a fluence ranging from <1 to >20 J/cm² (see Chung et al.¹).

Transcranial PBMT is a noninvasive light delivery method that is conducted by irradiation of the head using an external light source (laser or LEDs)². Fo....

Protocol

All of the procedures were carried out in conformity with the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health (NIH; Publication No. 85-23, revised 1985) and approved by the regional ethics committee of Tabriz University of Medical Sciences.

CAUTION: This protocol includes the application of Class 3B laser instruments and will require proper training and adherence to safety guidelines. Class 3B lasers can seriously damage the eyes and can heat the skin. Class 3B lasers are not considered a burn hazard. Eye protection goggles must be worn at all times when operating the laser device.

Results

Statistical analyses

The statistical analysis of data obtained from the Barnes training sessions was analyzed by two-way ANOVA; the other behavioral tests and analysis of hippocampal ATP levels among groups were carried out by one-way ANOVA, followed by Tukey's post hoc test. All data are expressed as means ± the standard error of the mean (SEM), except for the laser transmission data, which are shown a.......

Discussion

We describe a protocol for conducting a transcranial PBMT procedure in mice. This protocol is specifically targeted to neuroscience laboratories that perform photobiomodulation research focused on rodents. However, this protocol can be adapted to other laboratory animals that are frequently used in the neuroscience field, such as rabbit, cat, dog, or monkey.

Currently, there is increased interest in investigating transcranial PBMT with red/NIR lasers and LEDs. In order to successfully carry ou.......

Materials

Name	Company	Catalog Number	Comments
Ketamine	Alfasan	#1608234-01
Xylazine	Alfasan	#1608238-01
Agarose	Sigma	#A4679
Superglue	Quickstar
Vibratome	Campden Instruments	#MA752-707
Optical glass	Sail Brand	#7102
Power meter	Thor labs	#PM100D
Photodiode detector	Thor labs	#S121C
Caliper	Pittsburgh
GaAlAs laser	Thor Photomedicine
Etho Vision	Noldus
Centrifuge	Froilabo	#SW14R
Earmuffs	Blue Eagle
Digital camera	Visionlite	#VCS2-E742H
Sterio amplifier	Sony
Ethanol	Hamonteb	#665.128321
Barnes maze	Costom-made
ATP assay kit	Sigma	#MAK190
Elisa reader	Awareness	#Stat Fax 2100