Photobiomodulation Therapy for an Ischemic Olfactory Dysfunction Model

Abstract

Older people are at high risk of developing chronic neurodegenerative diseases, including Alzheimer’s disease, vascular dementia, and Parkinson’s disease. Vascular dementia is the second most common type of dementia due to impaired blood flow to the brain. The early stage symptom of vascular dementia is olfactory dysfunction. This study developed a mouse model of olfactory dysfunction based on photothrombosis (PT) over the olfactory bulb. Photobiomodulation (PBM) describes the therapeutic use of red or near-infrared light to stimulate healing, relieve pain and inflammation, and prevent tissue from dying. We applied photobiomodulation (PBM) in the acute phase of ischemia to improve the olfactory bulb function (OBF). The PBM was performed daily from day two until day seven after PT with the 808 nm laser with a fluence of 30 J/cm2 per day (irradiance of 250 mW/cm2 for 2 minutes per day). Buried food test was used as a behavioral test to assess the olfactory function before PT, after PT, and after PBM. To quantify the OBF, we performed the buried food test on the food-deprived mice. Furthermore, we performed hematoxylin and eosin (H&E) staining after harvesting the brain on day eight to correlate the buried food test results and histological changes in the OB. Our finding indicates that PBM therapy may improve the olfactory function in the acute phase of ischemia.