Thèse Effet de la Perte d'Orexine sur la Dérégulation Émotionnelle dans la Narcolepsie H/F - Doctorat.Gouv.Fr

Établissement : Université Claude Bernard Lyon 1 École doctorale : NSCo - Neurosciences et Cognition Laboratoire de recherche : CRNL - CENTRE DE RECHERCHE EN NEUROSCIENCES DE LYON Direction de la thèse : Christelle PEYRON ORCID 0000000293173546 Début de la thèse : 2026-10-01 Date limite de candidature : 2026-05-31T23:59:59 La narcolepsie de type 1 (NT1) est un trouble neurologique caractérisé par une somnolence diurne excessive et la cataplexie, une perte soudaine du tonus musculaire déclenchée par des émotions positives intenses telles que le rire ou la surprise. Il est intéressant de noter que les circuits neuronaux de l'amygdale présentent des épisodes d'hyperactivité en réponse à des stimuli émotionnels positifs chez les patients atteints de NT1. Cependant, les mécanismes sous-jacents restent largement inexplorés. Déterminer les dysfonctionnements de la dynamique neuronale au sein du réseau local du complexe basolatéral de l'amygdale (BLA), dans un modèle murin de NT1, pourrait permettre d'identifier et de cibler des populations neuronales spécifiques afin de restaurer un sommeil et une fonction émotionnelle normaux.
Il est désormais établi que la NT1 est causée par la perte de neurones excitateurs à orexine (hypocrétine), dont la déficience entraîne une dérégulation des cibles en aval, notamment le complexe basolatéral de l'amygdale (BLA).

L'objectif de ce projet est de décrypter l'effet de la déficience en orexine sur la dérégulation du traitement émotionnel dans le BLA de souris NT1 inductibles. Notre objectif est de déterminer comment l'activité neuronale du noyau basolatéral de l'amygdale (BLA) est altérée suite à l'ablation rapide des neurones à orexine. Grâce à l'imagerie calcique biphotonique, nous suivrons longitudinalement l'activité des microcircuits du BLA avant et après l'apparition de la maladie afin d'identifier d'éventuelles altérations de la dynamique neuronale en réponse à des stimuli émotionnels positifs et négatifs.
Dans une seconde expérience, nous testerons si la manipulation chémogénétique des neurones altérés pourrait restaurer le sommeil et la fonction émotionnelle. Narcolepsy type 1 (NT1) is a neurological disorder characterized by excessive daytime sleepiness, fragmented sleep, rapid eye movement (REM) sleep dysregulation and cataplexy, a sudden loss of muscle tone triggered by strong positive emotions such as laughter or surprise [1].
Interestingly, neuronal circuits within the amygdala display bouts of hyperactivity in response to positive emotional stimuli in NT1 patients [2]. However, the underlying mechanisms remain largely unexplored.
It is now established that NT1 is caused by the loss of wake-promoting/REM sleep inhibiting orexin (hypocretin) neurons [3; 4]. Orexin neurons are excitatory neurons whose deficiency leads to dysregulation of downstream targets, including the basolateral complex of the amygdala (BLA) [5-7]. Determining the neuronal dynamics dysfunctions in the local BLA network, in a mouse model of NT1, could allow us to identify and target specific neuronal populations in order to restore proper sleep and emotion function. The project focuses on the effect of orexin deficiency on emotional processing dysregulation in NT1.
Based on the well-known modulatory role of orexin on the extensive limbic circuits [8], we propose that orexin loss causes a functional imbalance in BLA microcircuits, by reducing the activity of parvalbumin (PV) inhibitory neurons of the BLA, the main source of inhibition of PYR excitatory cells, leading to PYR hyperexcitability. This unbalance would favor NREM to REM transitions and trigger cataplexy during positive emotional cues. Negative-valence pathways, being anatomically and functionally distinct, may be less affected. To test this hypothesis, we will investigate how orexin loss disrupts neural dynamics within the BLA.
Aim 1: Deciphering BLA neuronal dynamic in health and disease. This project aims to determine how, neuronal activity in the BLA is altered following the induction of NT1 in mice. Using two-photon calcium imaging in a novel mouse model of NT1, where rapid orexin neuron ablation is inducible [4], we will longitudinally monitor BLA microcircuit activity before and after disease onset to identify putative alterations in neuronal dynamics in response to both positive and negative emotional stimuli as well as during sleep.
Aim 2: Restoring BLA activity in NT1 mice. To determine whether the negative effects of orexin loss on the BLA neural dynamics can be reversed, we will selectively chemogenetically activate (hM3Dq) PV neurons within the BLA to test whether stimulating PV cells can rescue BLA function. To investigate how orexin loss affects neuronal activity in the BLA and leads to emotional dysregulation, we will perform a longitudinal, within-subject study combining behavioral assessment of cataplexy and two-photon (2P) calcium imaging in OX-DTR::PV-Cre mice [11,12]. To identify cell-type-specific activity, AAV-DIO-tdTomato virus will be co-injected with AAV- hSyn-GCaMP (green shifted calcium indicator in all neurons) in the BLA of OX-DTR::PV-Cre mice. PV interneurons will be specifically labeled (red) enabling their identification among the broader recorded population of GCaMP-expressing neurons (green). Baseline polysomnographic (EEG/EMG) recordings in freely moving mice will first be used to characterize normal sleep-wake cycles and absence of cataplexy. Subsequently, 2P- calcium imaging sessions will be conducted to investigate neuronal firing patterns across sleep phases and during exposure to emotionally salient stimuli: chocolate (positive [9]) and quinine (negative [10]). EEG/EMG signals will be recorded concurrently during all imaging sessions to enable precise sleep-stage classification and correlate neural activity with vigilance states.
Next, orexin neurons will be selectively ablated by DTX administration. Five days later, cataplexy onset will be verified [9], followed by 2P-calcium imaging sessions targeting the same neurons as in baseline sessions. It will assess changes in activity after orexin depletion compared to baseline. Imaging will be performed for three consecutive days at each experimental stage (baseline vs post-DTX) to ensure stable, reproducible results. If cataplexy is not detected at this early stage, the procedure will be repeated 6 weeks later.
In a second experiment we will assess whether chemogenetic activation of BLA PV interneurons can reverse the occurrence of cataplexy triggered by chocolate ingestion.

expérience en imagerie calcique bienvenue,
neurosciences
Formation éthique en expérimentation animale
Programmation en Python ou Matlab serait un plus