Transcranial near-infrared phtobiomodulation causes anti-depressive and anti- anxiety effects in mice model of depression

Introduction: Depression is a common psychiatric disorder and about one in five people experience depression during their lifespan. Despite the anti-depressive effects of drug therapy, problems such as non-targeting and dose-resistant lead to more effective approaches. Transcranial Photobiomodulation (TPBM) or transcranial low-level laser (TLLL) therapy is a novel and neuroprotective approach which its therapeutic potential has been experimentally examined for central nervous system disorders such as stroke, traumatic brain injury, Alzheimer disease, and Parkinson disease. In this safe and non-heating approach, the damaged and troubled brain areas are irradiated transcranially by near- infrared (NIR) and red (600-1100 nm) low power (less than 500 mW) diode lasers, lasers, and light emitting diodes. The functional mechanism in this approach is that NIR and red photons are absorbed by photo-receptors such as cytochrome c oxidase (COX) and then a number of biological processes including mitochondrial respiratory chain and ATP synthesis are accelerated and cause modulatory effects on nerve cells activities. The main goals of the current study are to examine the anti-depressive and anti-anxiety effects of NIR TPBM by behavioral tests including open field test (OFT), and elevated plus maze (EPM) test in mice model of depression. Materials and Methods: Thirty-three (eight- to ten-week-old) BALB/c male mice were used for all experiments. Mice were obtained from animal lab of Tabriz University of Medical Sciences. One week before the experiments began, all animals were housed in standard conditions of dark/light cycle (12h/12h), humidity (40-50%), and temperature (20-23 °C). Then mice were divided into three groups (11 per group): control, stress (sham), and near-infrared treated (NIRT) groups. To induce stress, sham and NIRT mice were trapped in a 50 ml polypropylene cylinder for three continuous weeks (3h/day). NIRT group received simultaneous laser treatment with stress induction, however, laser probe was placed on the skull of sham mice, but irradiation was not done. For TPBM therapy a GaAlAs diode laser (810nm, 10 Hz, 88% duty cycle, and power density of 4.75 J/cm2) was used and irradiation was done on odd days and continued for three weeks (nine treatment sessions in total). At each session of laser therapy, 8 J/cm2 dose of NIR light was delivered to the brain cortex of NIRT mice. At the end of stress procedure, behavioral tests including OFT, and EPM were performed to evaluate the anti-anxiety and anti-depressive effects of TPBM and The underlying variables were calculated: time spent in the center square of the OFT, and both percentage of time spent in the open arms (%OAT), and percentage of open arm entries (%OAE) in the EPM. Results: Sham mice which underwent to stressful conditions showed significantly (p<0.001) less tendency to spent time in the center part of the OFT in comparison to control group. Furthermore, %OAT and %OAE were significantly (p<0.001) declined in the sham group. The bad effects of stress procedure declined by TPBM so that NIRT mice indicated a more significant (p<0.01) tendency to spent time in the center square of the OFT. In addition, %OAT (p<0.0001) and %OAE (p<0.001) significantly increased in NIRT group. Conclusion: In this study, OFT and EPM were performed to examine the anti-depressive and anti-anxiety effects of TPBM, respectively. Our results indicated that TPBM decreased depressive-like behaviors and NIRT mice significantly tended to spend more time in the middle part of the OFT. In addition, %OAT and %OAE were significantly improved by TPBM which indicated a reduction in anxiety-like behaviors. As a whole, this study indicates that TPBM is a novel approach to depression improvement which can enhance depressive- and anxiety-like behaviors.