Venue: Centre Broca
Marco Canepari
Laboratoire Interdisciplinaire de Physique (LIPhy)
Université Grenoble Alpes et CNRS UMR 5588
http://marco-canepari.wix.com/neuron-imaging-team
Title
Optical analysis of neuronal ionic currents in acute brain slices and its application to the study of channelopathies
Abstract
Neurons are spatially-complex cells where ionic currents cannot be measured using the patch clamp technique because the membrane potential (Vm) is not uniform. In our team, we developed techniques to measure optically Ca2+ currents [1] and Na+ currents [2] from various compartments of neurons in the native environment of the brain slice. These approaches are combined with Vm optical measurements using voltage-sensitive dyes, in order to correlate the behaviour of ion channels with the associated Vm change in the different compartments of interest. In addition, the use of selective pharmacology and of computational analysis using NEURON modelling allows dissecting the contribution of diverse ion channels involved in neuronal excitability as well as their functional synergistic interaction [3]. After introducing this powerful experimental approach, I will present a recent study where we demonstrated a novel role for the Nav1.2 voltage-gated Na+ channel as strong activator of the BK K+ channel during the process of activation of the action potential in the axon initial segment of neocortical pyramidal neurons [4]. As a follow-up of this study, I will present some preliminary data on animal models of autism carrying critical functional mutations of the SCN2A gene expressing the Nav1.2 channel, showing how we can significantly contribute to the understanding of these rare channelopathies as well as to the characterisation of novel therapeutic molecules. I will finally present another study where demonstrate that in the apical dendrite of the same neuron BK channels are instead selectively activated by N-type voltage-gated Ca2+ channels during the back-propagation of the action potential (paper under submission). The understanding of the interaction of BK channels and their different site-dependent Ca2+ source partner is fundamental at understanding channelopathies of this fundamental K+ channel.
[1] Jaafari N, De Waard M, Canepari M (2014) Biophys J 107 : 1280-1288.
[2] Filipis L, Canepari M (2021) J Physiol 599: 49-66.
[3] Ait Ouares K, Filipis L, Tzilivaki A, Poirazi P, Canepari M (2019) J Neurosci 39: 1969-81.
[4] Filipis L, Blömer LA, Montnach J, Loussouarn G, De Waard M, Canepari M (2023) J Physiol in press.