Soutenance de thèse – Tessa Scarabello

Venue: Centre Broca

Tessa Scarabello
IINS

Directrice de thèse : Lisa Roux

Titre

Olfaction and Oxytocin in female alloparental behaviors

Abstract

Alloparental behaviors de­ne the set of actions undertaken by adults to insure the survival of other individuals’ progeny such as crouching over the young, retrieval, or parental nesting. The very fi­rst encounter with a pup is able to trigger these behaviors in naive virgin mice and performances improve upon repeated exposures. Though, the neurobiological substrates of this phenomenon are still unclear. Previous work highlighted the importance of auditory cues and oxytocin (OT) release in the auditory cortex of virgin females for the establishment of retrieval behavior. Yet, the role played by olfaction in the transition of mice from naive to efficient caretakers so far remains little explored. The goal of this work was to assess the impact of olfaction in the establishment of parental nesting in naive female mice, as well as the influence of oxytocinergic neuromodulation in the olfactory piriform cortex (PIR).

Within just a few minutes, naive C57Bl6/J female mice exposed to pups start building a parental nest. We showed that masking pup odor delays the onset of nesting in these mice, highlighting the role of olfaction in triggering this behavior. Using immunochemistry in the Oxtr-3xHA-T2A-iCreERT2 mouse line, we showed that oxytocin receptors (OTR) are expressed in the deep layer of the PIR. To selectively suppress the expression of these receptors in the PIR and test the impact on nesting, we adopted a viral approach to express the cre-recombinase locally in the PIR of Oxtr[flox] mice. Similar to previous experiment with pup odor masking, this local knock-out of the OTR in the PIR impaired nesting behavior, compared to mice injected with a control virus. To assess the dynamics of OT signaling in the PIR during our task and in particular during pup olfactory investigation preceding the start of nesting, we monitored mice with fi­ber photometry using a recently designed OT GRAB sensor. Finally, using a cutting-edge brain clearing technique and brain-wide activity mapping (iDISCO), we compared the brains of naive females exposed for the fi­rst time to a pup with or without a local knock-out of the OTR in the PIR. We found differences at the level of deep brain structures such as the prefrontal cortex.

This work paves the way for future research to understand how olfaction and its modulation by OT shapes pup-directed behavioral changes in naive female mice.

Keywords: Alloparental behaviors; Oxytocin ; Olfaction

Jury

• Mme BUONVISO Nathalie, DR, CRNL, Lyon – Rapportrice
• Mme CARCEA Ioana, AP, Rutgers Brain Health Institute, N.J – Rapportrice
• Mme MUSCATELLI Françoise, DR, INMED, Marseille – Examinatrice
• M.  RENIER Nicolas, DR, ICM, Paris – Examinateur
• Mme ROUX Lisa, DR, IINS, Bordeaux – Directrice de thèse
• M. FERREIRA Guillaume, DR, INRAE, Bordeaux – Invité