Evaluating safe infrared neural stimulation parameters: Calcium dynamics and excitotoxicity thresholds in dorsal root ganglia neurons

作者：Parinaz Abdollahiyan, Kunyang Sui, Guanghui Li, Rune W. Berg, Marcello Meneghetti, Christos Markos · 发表于：Journal of Neuroscience Methods · 年份：2025 · DOI：10.1016/j.jneumeth.2025.110484 · 被引用次数：3 · 研究领域：Photoreceptor and optogenetics research、Laser Applications in Dentistry and Medicine、Ocular and Laser Science Research

BACKGROUND: As a promising neural stimulation technique, infrared neural stimulation (INS) has recently gained significant attention due to its ability to stimulate neuronal activities without needing exogenous agents. NIR light is absorbed by water of the tissue producing local thermal effects. Therefore, INS is a suitable candidate for localized and targeted neural stimulation. However, despite the wide variety of research studies on INS applications, limited studies have focused on identifying and optimizing the stimulation parameters to avoid potential excitotoxicity. This study evaluates the dorsal root ganglia (DRG) neurons' response under INS with varying intensities and illumination time. NEW METHOD: Here, DRG neurons are cultured and labeled by the CamkII-GCaMP6s virus. The neurons were exposed to infrared laser pulses (2.01 µm wavelength, different powers of 2.5 mW, 5 mW, 7.5 mW, and 10 mW) for durations of 300 s and 400 s. The light was delivered through a silica optical fiber aligned and stabilized within a free-space optical setup. Simultaneous with INS, neuronal activity was evaluated by calcium imaging through a fluorescence microscope. This method allowed real-time monitoring of neuronal calcium dynamics under different stimulation conditions, preparing an overview of the safe thresholds for INS. RESULTS: It was found that calcium saturation has happened for the neurons in exposure to light intensities (7.5 mW and 10 mW) for 300 s, representing potential excit...