Automated Transcranial Photobiomodulation in Healthy Rats: Effects on Working Memory and Brain Markers

Abstract

Photobiomodulation (PBM) uses red and near-infrared light to stimulate biological processes through cytochrome c oxidase (CCO) activation, enhancing ATP synthesis and neuroprotection. This study evaluates the PBM effects on spatial working memory (WM) and cellular mechanisms in healthy adult male rats, focusing on CCO activity, c-Fos, and synaptogenesis-related proteins. PBM (810 nm, 40 Hz, 20 J cm⁻²) is applied for five consecutive days (PBM-C) or five alternating days (PBM-A). PBM improves spatial WM in both groups compared to controls. CCO activity decreases in the prefrontal and retrosplenial cortex, as well as in the hippocampus, suggesting more efficient energy use during cognitive tasks. PBM increases c-Fos expression in the prefrontal and parietal cortex, reflecting heightened neuronal activity. Synapsin-I levels rise in the prefrontal cortex for both protocols, while PBM-C increases PSD-95 in the hippocampus. GFAP expression decreases in cortical regions with both protocols, while PBM-C increases it in the prefrontal cortex. These findings suggest that PBM PBM-C enhances prefrontal and hippocampal synapses, potentially underlying observed WM improvements. This study highlights the PBM potential in modulating CCO activity and synaptic plasticity, providing a basis for identifying effective schedules and targets for WM preservation and treatment.