How infrared transcranial laser photobiomodulation affect chronic stress-induced learning and memory impairment in comparison with methylene blue in mice

Background and Aim : Methylene-blue (MB) and transcranial Photobiomodulation (tPBM) protect neural cells by stimulating the mitochondrial function. Both of these interventions force the complex IV of the electron transport chain. In this study, we examined the effects of tPBM and MB alone or combined with each other in chronic stress-induced learning and memory impairment.Methods : Animals were randomly assigned into 5 groups (12 BALB/c mice in each group) (i) control , (ii) laser Sham + normal saline (NS) , (iii) tPBM + NS , (iv) laser Sham + MB and (v) tPBM + MB . All animals, rather than animals in the control group, were undergone unpredictable chronic mild stress (UCMS) conditions for 4 weeks. At the same time, the treatments involved tPBM (810 nm, 10Hz pulsed, 8 J/cm2 each section; three times per week) and MB (daily intraperitoneal, 0.5 mg/kg) were administered in corresponding groups. The anxiety was measured by the elevated plus maze (EPM) test. Also, learning and memory performance were measured by novel object recognition (NOR) and Barnes maze tests. The molecular levels of nitric oxide (NO) in brain tissue and serum levels of cortisol were measured by spectrophotometric methods.Results : Results of EPM tests revealed that UCMS caused anxiety-like behaviors by decreasing the Open Arena Entrance (%OAE) and Open Arena Time (%OAT). Learning and memory impairments were also observed in NOR and Barnes maze tests. The exploration time of the novel and familiar objects were the same in the Sham + NS group. Also, the discrimination index (DI) of the Sham + NS group in the NOR test was also significantly less than the control group. Time spent in the target quadrant and correct/wrong relative time was also significantly decreased in the Sham + NS group compared to control animals. Treatment with tPBM and MB alone or in combination has significantly returned these behavioral impairments to normal conditions. The levels of NO in the brain as well as serum cortisol levels significantly increased in the laser sham + NS animals compared to the control group. tPBM and MB treatments were capable of reversing these changes to normal conditions.Conclusion : Treatment with tPBM and MB alone or in combination showed significant therapeutic effects on learning and memory impairments under UCMS conditions. The improvements in tPBM + MB group were also the same as single treatments. This could be due to the fact that single treatments completely reversed the damage of UCMS to normal conditions and the combined treatment could not go more ahead.

کلیدواژه ها:

Transcranial Photobiomodulation ، Methylene Blue ، Unpredictable chronic mild stress ، Learning and Memory