ED Sciences de la Vie et de la Santé
Characterization of the molecular determinants of behavioral changes induced by ketamine at the nanoscale
by Floriane UYTTERSPROT (Institut Interdisciplinaire de Neurosciences)
The defense will take place at 14h00 - Salle de conférence CGFB Centre de Génomique Fonctionnelle Bordeaux (CGFB) 146 Rue Léo Saignat 33000 Bordeaux
in front of the jury composed of
- Julien DUPUIS - Chargé de recherche - Université de Bordeaux - Directeur de these
- Stéphane OLIET - Directeur de recherche - Université de Bordeaux - Examinateur
- Julie PERROY - Directrice de recherche - Université de Montpellier - Rapporteur
- Ana Luisa CARVALHO - Professeure des universités - University of Coimbra - Rapporteur
- Thomas FRERET - Professeur des universités - Université de Caen - Examinateur
N-methyl-D-aspartate glutamate receptors (NMDAR) are key actors of excitatory neurotransmission. By allowing calcium influx and subsequent activation of signaling pathways, NMDAR play a central role in synaptic plasticity events that occur during development and underlie cognition and memory processes. Consequently, NMDAR dysfunctions are associated with neurological and psychiatric conditions such as Alzheimer's disease, psychotic disorders or major depressive disorder, a leading cause of disability worldwide that is believed to be the consequence of abnormal activity in cortico-meso-limbic structures supporting mood and reward. While efforts to develop compounds modulating NMDAR activity for therapeutic applications have allowed the discovery of drugs of major medical value such as ketamine (anesthetic, antidepressant) or memantine (cognitive enhancer), their clinical use is often limited by severe adverse effects and several questions regarding their action mode remain unanswered. Recent advances in super resolution microscopy have revealed that NMDAR adopt a precise and dynamically regulated nanoscale organization at synapses. Beyond ionotropic considerations, this organization regulates NMDAR-dependent signaling and plasticity and controls memory formation. Furthermore, pathological alterations to this unexpected dimension of NMDAR signaling have been associated with several brain disorders, thereby raising the question whether NMDAR synaptic organization could represent a therapeutic target of interest. In order to address this question, we used a combination of whole-brain imaging, super resolution microscopy, functional imaging, biochemistry and behavioral approaches to perform a multiscale dissection of the action mechanisms of clinically-relevant NMDAR antagonists. We demonstrate that the open-channel blocker ketamine promotes interactions between NMDAR and PDZ domain-containing scaffolding proteins and enhances NMDAR trapping at synapses. We further show that ketamine-elicited trapping enhancement compensates for depletion in synaptic receptors triggered by autoantibodies from patients with anti-NMDAR encephalitis, mitigates impairments in NMDAR-mediated CaMKII signaling, and alleviates anxiety- and sensorimotor gating-related behavioral deficits provoked by autoantibodies. Following these findings, we further examined whether ketamine-elicited changes in NMDAR synaptic organization may contribute to the rearrangements in brain connectivity supporting its antidepressant properties using a pharmacological model of depression based on chronic corticosterone administration. Detection of immediate early gene expression in transparised brains using light-sheet microscopy revealed rewiring in prefrontal cortical networks both in animals chronically exposed to corticosterone that displayed anxiety/depression-like manifestations, and after administration of subanesthetic doses of ketamine producing antidepressant actions. Synaptosomal fractionation on prefrontal cortical samples 24h after ketamine administration further showed that it compensated for decreased expression of key synaptic proteins like synaptophysin, and improved corticosterone-induced alterations in the ratio between synaptic GluN2A and GluN2B subunit-containing NMDARs. These ketamine-elicited redistributions of synaptic NMDAR likely resulted from subtype-selective changes in receptor trapping which may favor plasticity induction, as revealed by photoactivated localization microscopy experiments performed on dissociated cortical neurons, and explored in vivo using subtype-selective tools to prevent ketamine-induced NMDAR synaptic redistributions and assess their contribution to antidepressant responses. Overall, our results reveal unexpected molecular mechanisms supporting the psychoactive properties of ketamine, and highlight the potential of targeting receptor synaptic organization as a therapeutic strategy for NMDAR hypofunction-related mental disorders.
ED Sciences Physiques et de l'Ingénieur
Femtosecond laser-matter interaction study of gap materials in GHz burst-mode
by Pierre BALAGE (Centre Lasers Intenses et Applications)
The defense will take place at 10h00 - Amphithéâtre IOA Institut d'Optique d'Aquitaine 1 Rue François Mitterrand 33400 Talence
in front of the jury composed of
- Inka MANEK-HÖNNINGER - Professeure des universités - Université de Bordeaux - Directeur de these
- Stefan NOLTE - Professor - Friedrich-Schiller-Universität Jena - Rapporteur
- Razvan STOIAN - Directeur de recherche - Université Jean Monnet - Rapporteur
- Ottavia JEDRKIEWICZ - Docteure - CNR-Istituto di Fotonica e Nanotecnologie - Examinateur
- Philippe BALCOU - Directeur de recherche - Université de Bordeaux - Examinateur
Over the past two decades, femtosecond laser technology has become significantly more reliable which has particularly enabled its integration into industry, as the brevity of such pulses allows for high-precision micromachining. However, the adoption of this technology in the industry remains hindered by a lack of productivity. Indeed, the production rate remains well below the ever-evolving industry targets. To address this limitation, several methods are being studied to increase the throughput by optimizing femtosecond laser processes. One approach relies on optimizing the energy deposition by using bursts of low-intensity femtosecond pulses rather than single high-intensity pulses. Recent studies have shown that using GHz-bursts can achieve ablation efficiencies far superior to those obtained with more conventional methods. However, these initial results have been quickly challenged by other studies reporting lower efficiency and the presence of machining defects. To reach a consensus on this new regime, comprehensive experimental studies are needed to add data to the current state of the art. To this end, process studies such as microdrilling experiments and cutting with a Bessel beam have been implemented using a 100 W Amplitude laser delivering GHz-bursts. Close collaboration with the company Amplitude has allowed for investigating numerous burst parameters and conducting comparative studies with existing regimes (single-pulse and MHz-bursts). Moreover, a pump-probe experiment has been set up revealing the laser-matter interaction mechanism in GHz-burst mode. Throughout this thesis work, excellent results have been obtained, demonstrating the unique capability of GHz-bursts for microprocessing materials like dielectrics and semiconductors.