Transcranial Photobiomodulation
IN THIS LESSON: MECHANISMS OF ACTION
The principal chromophore for NIR light in neural tissue is cytochrome c oxidase (CCO), the terminal enzyme of the mitochondrial respiratory chain.
Photon absorption dissociates inhibitory nitric oxide (NO) from CCO, increasing mitochondrial membrane potential, oxygen consumption, and ATP synthesis.
Laser-mediated NO release also relaxes vascular and lymphatic endothelium, increasing cerebral blood flow and activating the brain waste removal system via meningeal lymphatic vessels.
Preclinical laser studies further demonstrate
anti-inflammatory microglial polarization from M1 to M2 phenotypes
reduced oxidative stress
upregulation of brain-derived neurotrophic factor (BDNF), supporting neurogenesis and synaptic plasticity