Muenkel, C. | bioRxiv Science

bioRxiv2026

Ex vivo Infrared Nerve Stimulation on the Rat Sciatic Nerve: Challenges and Pitfalls

Infrared nerve stimulation (INS) offers millisecond-scale, electrical artifact-free activation of peripheral nerves, yet rat ex vivo studies remain scarce. We present an INS setup utilizing a lens system for free-beam focus for rat sciatic nerves partially submerged in a nerve bath, making re-wetting of the tissue in existing ex vivo INS setups redundant. Excised sciatic nerve preparations were illuminated at 1470 nm, delivering pulse trains from 100 - 2000 s at 5 Hz with radiant exposures up to 25.7 J/cm2. Compound action potentials (CAPs) were recorded with tungsten hook electrodes. Nerve activity could be recorded up to 200 minutes after excision, though persistent nerve excitability remained comparable to existing ex vivo studies as a yet to be optimized parameter. Peak CAP amplitudes ranged from 3.9 - 36.9 {micro}V with latencies averaged at 3.4 ms. Activation thresholds spanned 1.75 - 13.05 J/cm2. Additionally, potential pitfalls for INS setups and ways to resolve them were investigated, with two artifact types highly relevant to ex vivo INS being identified: A photo-thermal expansion artifact and a photovoltaic artifact with thermo-capacitive coupling. The observations confirm that CAPs can be evoked via INS in an ex vivo preparation of the rat sciatic nerve. The presented platform supports 3R principles and offers a robust basis for introduction of pharmacological investigations with INS.

neuroscience↗

bioRxiv2021

Transcriptional characterization of the glial response due to chronic neural implantation of flexible microprobes

Long term implantation of (micro-)probes into neural tissue cause unique and disruptive responses to these foreign bodies. In this study, we present the transcriptional trajectory of glial cells responding to chronic implantation of flexible micro-probes for up to 18 weeks. Transcriptome analysis shows a rapid activation of microglial cells and a strong upregulation of reactive astrocytic genes, which is lost over the full duration of the implant period. Most interestingly, animals that were implanted for 18 weeks show a transcriptional profile similar to non-implanted controls, with increased expression of genes associated with wound healing and angiogenesis, which raises hope of a normalization of the neuropil to the pre-injury state when using flexible probes. Nevertheless, our data show, that a subset of genes upregulated after 18 weeks belong to the family of immediate early genes, which would indicate that structural and functional remodeling has not been completed at this time point. Our results confirm and extend previous work on the molecular changes resulting from the presence of intraneural probes and provide a rational basis for developing intervention strategies to control them.

neuroscience↗