Effects of transcranial near-infrared photobiomodulation on electrical activity of hippocampal neurons in a rat model of Alzheimer's disease

Abstract

Alzheimer's disease is one of the most common causes of dementia in old age, so that about 50 million people around the world are suffering from dementia and 50-70% of them are suffering from Alzheimer's disease. Considering that the commonly used drugs are not effective due to side effects and various drug interactions, it seems necessary to use new treatment methods for the treatment of Alzheimer's disease. The present study was conducted to investigate the effect of transcranial near-infrared laser (PMB) radiation on changes in the electrical activity of single neurons in the hippocampus of Alzheimer's model rats to find a new treatment method. Materials and methods: 48 adult male Wistar rats (weighing 250-300 g) were used in this study. The animals were randomly divided into 6 groups of eight including control, surgical sham, Alzheimer's model (AD), AD+ treatment with PBM 8 J, AD+ treatment with PBM 16 J, and AD+ treatment with PBM 32 J. Alzheimer's model was induced by injecting amyloid beta (Aβ1-42) into the lateral ventricles of the brain. In the treatment groups, rats were exposed to 810 nm PBM with energies of 8, 16, and 32 joules daily for 14 consecutive days. Two weeks after the surgery, the T-Maze test was performed to check the animal's memory. At the end, the electrical activity of the hippocampal neurons was evaluated by the electrophysiology protocol, and the rate of nerve firing and the frequency of spike activities were recorded in different groups. Results: 8 J laser irradiation for 14 days in AD rats significantly improved the memory of AD animals in the T-Maze test compared to the AD group. Also, the results of single-unit electrophysiological recording showed that 8 J laser increases the rate of nerve firing and the frequency of spike activities in AD animals.