Venue: Centre broca
Defense in english
Thesis supervisor: Lisa Roux (IINS)
Title
Impact of oxytocin in the anterior piriform cortex and link with respiration
Abstract
Breathing is a highly dynamic process that varies in frequency and intensity. These variations are related to the emotional and cognitive state of the animal but also to the recruitment of its olfactory system for the detection of odorant molecules, as it is the case during social interactions between individuals. In addition, a growing body of evidence shows that breathing influences brain neuronal rhythms. In this context, having an accurate and reliable tool of respiratory activity in freely moving animals that is also compatible with neuronal recordings seems more relevant than ever. We have developed a technique to record nasal pressure in freely moving mice and have characterized this signal according to the state of vigilance of the animal (awake – non-REM sleep – REM sleep). Our research shows that each state is associated with a specific combination of parameters characterizing the respiratory signal. Moreover, the precision of this technique allowed us to highlight the presence of pauses in this signal (i.e. transient absence of airflow). These pauses are not insignificant since they dictate the frequency of breathing, the other components of the respiratory cycle (inhalation and exhalation) forming units of relatively fixed duration. Finally, based on this signal, we built an artificial neural network from annotated data, capable of predicting the vigilance state of a mouse based on recordings its nasal pressure.
In a second part of this thesis, we focused on the role of oxytocin in the piriform cortex during social behaviors. Oxytocin has been widely described as a pro-social neuropeptide that promotes interactions and social memory. In rodents, olfaction is the main sensory modality, of which the piriform olfactory cortex represents a major neural substrate. The piriform has an anatomy similar to that of the hippocampus and is involved in olfactory memory processes. Because the piriform cortex expresses a high density of oxytocin receptors and because it receives oxytocinergic afferents, we tested the hypothesis that oxytocin in the piriform cortex modulates sociability and social memory. With a pharmacological approach targeted on this cortex, we showed that oxytocin induces subtle but surprising effects. Indeed, blocking its receptor leads to a selective increase in certain types of social interactions and seems to increase the attraction towards olfactory social stimuli. However, no effect on social memory was observed under our conditions.
Finally, in a third part we started to dissect the mechanisms of action of oxytocin on the physiology of the piriform cortex. We show that the oxytocin receptor agonist leads to a decrease in the burstiness of a subtype of excitatory neurons, both in vitro and in vivo. We further show that oxytocin decreases the entrainment of piriform cortex neurons by respiration.
Key words = oxytocin, respiration, sociability, social memory, piriform
Publications
Nasal pressure dynamics reveal state-specific features of respiratory cycles in freely moving mice (En cours de soumission)
Jury
– Lisa Roux – Université de Bordeaux (Directrice de thèse)
– Stéphane Oliet – Université de Bordeaux (Président)
– Claire Martin – Université Paris Diderot (Rapportice)
– Alexandre Charlet – Université de Starsbourg (Rapporteur)
– Anne-Marie Mouly – Université de Lyon (Examinatrice)
– Guillaume Ferreira – Université de Bordeaux (Examintateur)
– Francoise Muscatelli-Bossy – Université de Marseille (Examinatrice)