Transcranial photobiomodulation with near-infrared laser induces analgesia in rats

Photobiomodulation (PBM), also known as low-level light/laser therapy (LLLT), has emerged as a novel non-invasive photonic-based approach to modulate diverse physiological and biological activities. To date, however, PBM applications for pain suppression have primarily relied on cutaneous irradiation (via the integumentary system) or visual exposure (via the visual system). In this study we delineated that transcranial PBM (tPBM) with a 1064 nm laser can effectively relieve pain in rats. We initially assessed the inhibition effect of 1064 nm tPBM on nociception behaviourally, followed by an investigation of the underlying mechanisms utilizing electrophysiological techniques. Specifically, enhanced local field potential (LFP) signals were observed in the cortical area following stimulation. Additionally, 1064 nm tPBM mitigated the elevated brain activity elicited by formalin injection and sustained the brain connectivity disrupted by nociceptive inputs. Collectively, all these findings shed light on 1064 nm tPBM-induced analgesia in rats, and advances in understanding its mechanisms consequently provide novel insights into the pain managements/interventions clinically. KEY POINTS: Transcranial photobiomodulation (tPBM) with a 1064 nm laser can alleviate pain. Increased LFP signals were observed in the cortical area after stimulation. tPBM reduced pain-induced brain hyperactivity and sustained brain connectivity. tPBM demonstrates potential as a non-invasive approach for pain management.