Neuronal cells’ calcium influx modulates in response to 940 nm laser irradiation

Purpose: This study investigated the effects of 940 nm laser irradiation on calcium influx in trigeminal ganglion neurons. To understand the cellular mechanisms underlying the analgesic effects of photobiomodulation therapy (PBMT), focusing on whether specific laser parameters can modulate neuronal calcium dynamics, which could reduce pain perception. Methods: Primary cultures of trigeminal ganglia neurons were obtained from C57Bl/6 mice. Neurons were subjected to laser irradiation using a 940 nm InGaAsP semiconductor diode laser with energy density of 9.15 and 17.14 J/cm². Changes in intracellular calcium levels were measured using calcium imaging. To evaluate µ-opioid receptor (MOR) activity in sensory neurons, Ca²⁺ imaging was performed to measure the inhibition of KCl-induced Ca²⁺ influx by a MOR agonist. Additionally, mitochondrial membrane potential (MMP) assays were conducted to assess cellular metabolic changes post-irradiation. Results: Laser irradiation at 65 J significantly reduced intracellular calcium levels immediately after application, with a 50% decrease observed compared to control (p < 0.05). The opioid receptor inhibition study showed lower activity in the laser treated groups compared to control, indicating a potential interaction between photobiomodulation and opioid receptor pathways. However, no significant differences were found in MMP assays between control and laser-treated groups. Our findings suggest that 940 nm photobiomodulation at 65 J effectively inhibits calcium influx in TG neurons, indicating its potential for pain management. Conclusion: This study provides preliminary evidence supporting the potential of 940 nm PBMT to modulate intracellular calcium levels in trigeminal ganglion neurons, which may contribute to its analgesic effects. While only one set of parameters was tested, the findings encourage further investigations aimed at optimizing laser settings and exploring the underlying cellular mechanisms. These results lay important groundwork for future translational studies on the clinical use of PBMT as a non-invasive alternative to pharmacological pain management.