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Un nerf est un organe de forme linéaire, présent dans le corps de la plupart des animaux eumétazoaires (Eumetazoa, ou métazoaires supérieurs), dont les mammifères et l'homme. En neuroanatomie, un nerf désigne un regroupement d'axones distinct traversant un tissu. Ces axones sont issus de neurones dont les corps cellulaires sont le plus souvent regroupés en ganglion. Les nerfs et les ganglions sont les composants anatomiques de base d'un système nerveux. Chez les vertébrés, la majorité des nerfs font partie du système nerveux périphérique, même si le terme peut être employé pour certains faisceaux d'axones du système nerveux central. La fonction d'un nerf est de transmettre un signal, ou stimulus, d'un tissu à un autre, au sein d'un organisme pluricellulaire. Ce message nerveux est de nature électrique. Il est constitué des potentiels d'action qui se déplacent le long des axones qui constituent le nerf. Ces potentiels se déplacent de proche en proche sur les axones non myélinisés,

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Three-dimensional multilayer concentric bipolar electrodes restrict spatial activation in optic nerve stimulation

Marta Jole Ildelfonsa Airaghi Leccardi, Eleonora Borda, Ricardo Camilo Moreira, Vivien Gaillet, Diego Ghezzi, Elodie Geneviève Zollinger

Objective. Intraneural nerve interfaces often operate in a monopolar configuration with a common and distant ground electrode. This configuration leads to a wide spreading of the electric field. Therefore, this approach is suboptimal for intraneural nerve interfaces when selective stimulation is required. Approach. We designed a multilayer electrode array embedding three-dimensional concentric bipolar (CB) electrodes. First, we validated the higher stimulation selectivity of this new electrode array compared to classical monopolar stimulation using simulations. Next, we compared them in-vivo by intraneural stimulation of the rabbit optic nerve and recording evoked potentials in the primary visual cortex. Main results. Simulations showed that three-dimensional CB electrodes provide a high localisation of the electric field in the tissue so that electrodes are electrically independent even for high electrode density. Experiments in-vivo highlighted that this configuration restricts spatial activation in the visual cortex due to the fewer fibres activated by the electric stimulus in the nerve. Significance. Highly focused electric stimulation is crucial to achieving high selectivity in fibre activation. The multilayer array embedding three-dimensional CB electrodes improves selectivity in optic nerve stimulation. This approach is suitable for other neural applications, including bioelectronic medicine.

IOP Publishing Ltd2022

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Remodeling of peripheral nerve ensheathment during the larval-to-adult transition in Drosophila

Soumya Banerjee, Kumar Vishal

Over the course of a 4-day period of metamorphosis, the Drosophila larval nervous system is remodeled to prepare for adult-specific behaviors. One example is the reorganization of peripheral nerves in the abdomen, where five pairs of abdominal nerves (A4-A8) fuse to form the terminal nerve trunk. This reorganization is associated with selective remodeling of four layers that ensheath each peripheral nerve. The neural lamella (NL), is the first to dismantle; its breakdown is initiated by 6 hours after puparium formation, and is completely removed by the end of the first day. This layer begins to re-appear on the third day of metamorphosis. Perineurial glial (PG) cells situated just underneath the NL, undergo significant proliferation on the first day of metamorphosis, and at that stage contribute to 95% of the glial cell population. Cells of the two inner layers, Sub-Perineurial Glia (SPG) and Wrapping Glia (WG) increase in number on the second half of metamorphosis. Induction of cell death in perineurial glia via the cell death gene reaper and the Diptheria toxin (DT-1) gene, results in abnormal bundling of the peripheral nerves, suggesting that perineurial glial cells play a role in the process. A significant number of animals fail to eclose in both reaper and DT-1 targeted animals, suggesting that disruption of PG also impacts eclosion behavior. The studies will help to establish the groundwork for further work on cellular and molecular processes that underlie the co-ordinated remodeling of glia and the peripheral nerves they ensheath. (c) 2017 Wiley Periodicals, Inc. Develop Neurobiol 77: 1144-1160, 2017

Wiley2017

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Optical cuff for optogenetic control of the peripheral nervous system

Léonie Asboth, Grégoire Courtine, Stéphanie Lacour, Frédéric Pierre Gérald Michoud, Loïc Sottas

Objective. Nerves in the peripheral nervous system (PNS) contain axons with specific motor, somatosensory and autonomic functions. Optogenetics offers an efficient approach to selectively activate axons within the nerve. However, the heterogeneous nature of nerves and their tortuous route through the body create a challenging environment to reliably implant a light delivery interface. Approach. Here, we propose an optical peripheral nerve interface—an optocuff—, so that optogenetic modulation of peripheral nerves become possible in freely behaving mice. Main results. Using this optocuff, we demonstrate orderly recruitment of motor units with epineural optical stimulation of genetically targeted sciatic nerve axons, both in anaesthetized and in awake, freely behaving animals. Behavioural experiments and histology show the optocuff does not damage the nerve thus is suitable for long-term experiments. Significance. These results suggest that the soft optocuff might be a straightforward and efficient tool to support more extensive study of the PNS using optogenetics.

2018

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