The preparation of oblique spinal cord slices for ventral root stimulation

Video Link: The video component of this article can be found at: https://www.jove.com/video/54525Electrophysiological recordings from spinal cord slices have proven to be a valuable technique to investigate a wide range of questions, from cellular to network properties. We show how to prepare viable oblique slices of the spinal cord of young mice (P2 - P11). In this preparation, the motoneurons retain their axons coming out from the ventral roots of the spinal cord. Stimulation of these axons elicits back-propagating action potentials invading the motoneuron somas and exciting the motoneuron collaterals within the spinal cord. Recording of antidromic action potentials is an immediate, definitive and elegant way to characterize motoneuron identity, which surpasses other identification methods. Furthermore, stimulating the motoneuron collaterals is a simple and reliable way to excite the collateral targets of the motoneurons within the spinal cord, such as other motoneurons or Renshaw cells. In this protocol, we present antidromic recordings from the motoneuron somas as well as Renshaw cell excitation, resulting from ventral root stimulation.Financial supports were provided by the Agence Nationale pour la Recherche (HYPER-MND, ANR-2010-BLAN-1429-01), the NIH-NINDS (R01NS077863), the Thierry Latran Foundation (OHEX Project), the French association for myopathy (grant number 16026) and Target ALS are gratefully acknowledged. Felix Leroy was the recipient of a "Contrat Doctoral" from the Ecole Normale Supérieure, Cachan.Peer reviewe

Extending Cable Theory to Heterogeneous Dendrites

Dendrites exhibit many types of electrical and morphological heterogeneities at the scale of a few micrometers. Models of neurons, even detailed models, rarely consider such heterogeneities. Small scale fluctuations in the membrane conductances and the diameter of dendrites are generally disregarded and spines merely incorporated into the dendritic shaft. Using the two scales method known as homogenization, we establish explicit expressions for the small scale fluctuations of the membrane voltage, and we derive the cable equation satisfied by the voltage, when these fluctuations are averaged out. We establish rigorously under which conditions an heterogeneous dendrite can be approximated by an homogeneous cable. We consider different distributions of synapses, orderly or random, on a passive dendrite, and we investigate when replacing excitatory and inhibitory synaptic conductances by their local averages leads to a small error in the voltage. This indicates in which regimes the approximations made in compartmental models are justified. We extend these results to active membranes endowed with voltagedependent conductances or NMDA receptors. Then, we show that a spiny dendrite behaves as a smooth dendrite when the conductance of the spine neck is large compared to the conductance of the synapses impinging on the spine head, but also in the opposite situation, when it is small compared to the synaptic conductance. In this last regime, the only effect of spines is to deliver an effective synaptic current to the dendrite. This suggests that pedunculated and stubby spines might play complementary roles in synaptic integration. Finally, we analyze how varicosities affect voltage diffusion in dendrites and discuss their impact on the spatiotemporal integration of synaptic input

[Environs d' Agadir-Founti] / levée par le captaine Lamotte d'Incamps

Échelle(s) : [Echelles diverses

[Environs d' Agadir-Founti] / levée par le captaine Lamotte d'Incamps

Échelle(s) : [Echelles diverses

Sensibilisation au syndrome psychotraumatique chez les demandeurs d 'asile (intérêt de la prise en charge et caractéristiques de cette entité à travers onze entretiens)

Les médecins généralistes dans leur cabinet, les médecins urgentistes, ou encore les médecins des différentes structures de soins dédiées aux plus démunis peuvent être amenés à prendre en charge des demandeurs d'asile (DA). Ces patients souffrent souvent de troubles psycho-traumatiques. Ce travail sensibilise à ces troubles et à leurs caractéristiques au sein de cette population ainsi que sur les bénéfices ressentis à la suite de soins adaptés, en termes de qualité de vie et d'intégration sociale. Il s'agit d'une étude qualitative, réalisée au cours de onze entretiens à travers lesquels nous retrouvons les différentes spécificités de ce syndrome chez les DA. Les patients décrivent un ensemble de symptômes qu'il faut savoir reconnaître pour dépister les troubles afin de les prendre en charge de façon appropriée. Par ailleurs, ces entretiens soulignent l'intérêt de ces soins, puisque l'on constate que les patients éprouvent, d'une part, une amélioration de leur quotidien et que, d'autre part le suivi permet une meilleure intégration grâce à l'évolution positive de nombreux symptômes handicapant dans ce domaine. De nombreux facteurs freinateurs interviennent dans cette démarche de soins. Il faut en effet considérer la dimension transculturelle inhérente à cette prise en charge, ainsi que le contexte social des patients. Ce travail illustre les principaux facteurs et permet d'ouvrir une discussion sur les tenants et les aboutissants de ce suivi particulier. Il permet également d'aborder certaines particularités de l'éthnopsychiatrie. La sensibilisation du corps médical aux troubles psycho-traumatiques permet de mettre en place les soins appropriés, bénéfiques aux patients.General practitioners in their offices, emergency physicians or those working in various structures dedicated to homeless can eventually take care of asylum migrants. These patients often suffer from psycho-traumatic disorders. This work emphasizes these troubles and their characteristics in this specific population, as well as the benefits of adapted cares on their quality of life and social integration. This qualitative study was conducted through eleven asylum migrant s interviews during which we have found various specificities of psycho-traumatic disorders. Those patients describe a set of symptoms that need to be identified before naming the troubles and be able to cure them in the most appropriate way. In addition, these interviews highlight the benefit of the cares as patients mention improvements in their daily life. It also appears that a better social integration can be noticed through the positive evolution of numerous symptoms disabling in that field. Numerous slowing factors impact the care process. One has indeed to considerate the transcultural dimension of this handover as well as the social environment of the patients. This work illustrates the main factors and opens the debate on the ins and outs of this particular care. It also allows an approach to certain ethno psychiatry peculiarities. Improving awareness regarding psycho-traumatic disorders allows setting appropriate cares, proven to be beneficial to asylum migrant patients.ANGERS-BU Médecine-Pharmacie (490072105) / SudocSudocFranceF