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Laboratory of Neuronal Excitability



Our overall aim is to understand the nanoscale physiology of the brain. Hereunder the role of the brain’s extracellular space (ECS) in signaling and metabolite clearance, and the integrated regulation by multiple partners of synaptic signaling, beyond the mere pre- and post-synapse pair.

The ECS is the last major terra incognita of the nervous system; a fascinating, huge unknown that holds great promise for groundbreaking discoveries. The geometric structure of the ECS remains enigmatic, though it must inevitably reflect the extreme morphological complexity of its resident cells. All vacant ECS is filled by interstitial fluid, and the interstitial fluid compartment structurally corresponds to the ECS, which we utilize to visualize it through the recent super-resolution shadow imaging (SUSHI) approach. Research has provided volume-averaged values of the ECS volume fraction of around 10-30% of brain volume, though there is bound to be huge variation in smaller areas, where diffusion rates and directions will be increasingly dictated by ECS geometry. These diffusion properties remain unknown, largely due to lack of knowledge about ECS geometry and dynamics that prevents basic observations and biophysical modelling. Understanding the ECS entails also the outlining neural cells, and we investigate the ECS in the context of the diverse resident neural cells.
A parallel research focus is the specific roles of the multiple partners involved in regulating synaptic signals, with a focus on dendritic spines. Glutamatergic synapses on dendritic spines are tuned by multiple players, including the pre- and postsynaptic partners, astrocytic processes, and microglia processes. The functional parameters of these are commonly attributed to vesicular release properties or active membrane properties, such as receptors, transporters or channels. Notably, passive parameters afforded by the membrane, such as membrane topology and the perisynaptic ECS structure are largely disregarded. Yet, all synaptic signaling between neurons must inevitably pass via the ECS, yet the role of the ECS in shaping such signals is very poorly understood. Understanding the integrated mechanisms of synaptic signaling is at the core of understanding the brain, in health and disease, and is a main aim of ours.
To pursue these research lines we combine electrophysiology and fluorescence imaging in live brain slices, allowing us to read out structure and function. We are enabled by our expertise in super-resolution STED microscopy, and our implementation of this technique in our lab.



Our work relies primarily on electrophysiology and fluorescence imaging approaches in live tissue. Among the core techniques in our toolbox are electrophysiological whole-cell patch-clamp and field recordings, 2-photon imaging, STED microscopy, and optogenetics.



Principal Investigator

Latest publications

  1. Local diffusion in the extracellular space of the brain

    Tønnesen, Jan; Hrabĕtová, Sabina; Soria, Federico N.
    Neurobiology of Disease (Feb, 2023) DOI: 10.1016/j.nbd.2022.105981
  2. Transfer of the full SCN1A coding sequence to the brain of adolescent mice model of Dravet syndrome improves epileptic, motor and behavioral manifestations

    Mora-Jimenez, Lucia; Valencia, Miguel; [...] Ricobaraza, Ana; Hernandez-Alcoceba, Ruben
    Molecular Therapy - Nucleic Acids (Sep, 2021) DOI: 10.1016/j.omtn.2021.08.003
  3. Super-resolution STED microscopy in live brain tissue

    Calovi, S.; Soria, F.N.; Tønnesen, J.
    Neurobiology of Disease (Aug, 2021) DOI: 10.1016/j.nbd.2021.105420
  4. P2X7 Receptor-Dependent Layer-Specific Changes in Neuron-Microglia Reactivity in the Prefrontal Cortex of a Phencyclidine Induced Mouse Model of Schizophrenia

    Calovi, Stefano; Mut-Arbona, Paula; Tod, Pál; Iring, András; Nicke, Annette; Mato, Susana; Vizi, E. Sylvester; Tønnesen, Jan; Sperlagh, Beata
    Frontiers in Molecular Neuroscience (Nov, 2020) DOI: 10.3389/fnmol.2020.566251