Biology subjects

Gaiarsa, J.-L.

Publications and source records attributed to Gaiarsa, J.-L..

5 recordsLinked to original sources

bioRxiv2025

Inhibition of oxytocin neurons during key periods of development has long-term behavioural and body composition effects

BackgroundOxytocin (OT) is a key neuromodulator of social behavior in mammals, and accumulating evidence supports the existence of a critical period for OT action during infancy. However, other developmental windows remain poorly explored, and it remains unclear whether OT exert distinct functions depending on the timing of its activity. In this study, we aimed to determine whether specific developmental stages exist during which OT-expressing neurons play a decisive role with long-term consequences. MethodsWe used a chemogenetic approach to transiently inhibit OT-expressing neurons during three postnatal developmental periods: infancy, the juvenile period, and young adulthood in male and female mice. Behavioral and metabolic outcomes were then assessed longitudinally. We also examined the effects of inhibiting OT neurons during late fetal stages and at birth. ResultsSocial memory was consistently impaired in males, regardless of the timing of neuronal inactivation. The most pronounced behavioral effects were observed following inhibition during infancy in both sexes. Metabolically, adult males from all cohorts exhibited increased body weight, whereas increased fat mass and adipocyte size hypertrophy were specifically observed following inhibition during the juvenile period. Notably, inhibition of OT-expressing neurons around the time of birth resulted in delayed parturition and altered neonatal feeding behavior. LimitationsOT-expressing neurons release multiple signaling molecules. However, converging evidence suggests that the observed phenotypes are primarily attributable to OT deficiency. Although this study demonstrates long-term behavioral and metabolic consequences of transient OT neuron inhibition, further experiments are required to elucidate underlying mechanisms and identify additional effects. ConclusionsTransient inhibition of OT-expressing neurons during distinct postnatal developmental periods leads to long-lasting effects on social behavior and metabolism, with outcomes depending on both the timing of inhibition and sex. Furthermore, our findings reveal an unexpected role for fetal/neonatal OT neurons in regulating the timing of birth and early feeding behavior.

neuroscience↗

bioRxiv2023

Leptin antagonism improves Rett syndrome phenotype in symptomatic male Mecp2-null mice.

Rett syndrome (RTT) is a severe X-linked neurodevelopmental disorder caused by mutations in MECP2. Elevated circulating levels of the adipocyte hormone leptin are consistently observed in patients and in mouse models, yet their contribution to disease progression has remained unclear. Here, we show that reducing leptin signaling--either pharmacologically or genetically-- significantly alleviates RTT-like phenotypes in Mecp2-deficient mice. In males, these interventions preserved general health, prevented weight loss, and improved breathing and locomotor functions. At the neuronal level, they restored excitatory/inhibitory balance in the hippocampus and somatosensory cortex and rescued hippocampal synaptic plasticity. In females, delaying the pathological rise of leptin levels postponed symptom progression. These findings uncover leptin as a key contributor to RTT pathophysiology and position leptin-targeted interventions as a promising therapeutic strategy for this currently untreatable disorder.

neuroscience↗

bioRxiv2020

Acute neonatal oxytocin impacts hippocampal network development and restores adult social memory deficits in a mouse model of autism spectrum disorder.

Oxytocin is a master regulator of the social brain. In some animal models of autism, notably in Magel2 tm1.1Mus-deficient mice, peripheral administration of oxytocin in infancy improves social behaviors until adulthood. However, neither the mechanisms responsible for social deficits nor the mechanisms by which such oxytocin administration has long-term effects are known. Here, we aimed to clarify these oxytocin-dependent mechanisms focusing on social memory performance. We showed that Magel2tm1.1Mus-deficient mice present a deficit in social memory and studied the hippocampal circuits underlying this memory. We showed a co-expression of Magel2 and oxytocin-receptor in the dentate gyrus and CA2/CA3 hippocampal regions. Then, we demonstrated: an increase of the GABAergic activity of CA3-pyramidal cells associated with an increase in the quantity of oxytocin-receptors and of somatostatin interneurons. We also revealed a delay in the GABAergic development sequence in Magel2tm1.1Mus-deficient pups, linked to phosphorylation modifications of KCC2. Above all, we demonstrated the positive effects of subcutaneous administration of oxytocin in the mutant neonates, restoring neuronal alterations and social memory. Although clinical trials are debated, this study highlights the mechanisms by which peripheral oxytocin-administration in neonates impacts the brain and demonstrates the therapeutic value of oxytocin to treat infants with autism spectrum disorders.

neuroscience↗

bioRxiv2019

Characterization and rescue by oxytocin of an atypical thermo-sensory reactivity in neonatal mice lacking the autism-associated gene Magel2.

Atypical responses to sensory stimuli are considered as a core aspect and early life marker of autism spectrum disorders (ASD). Although recent findings performed in mouse ASD genetic models report sensory deficits, these were explored exclusively during juvenile or adult period. Whether sensory dysfunctions might be present at the early life stage and rescued by therapeutic strategy are fairly uninvestigated. Here we identified that neonatal mice lacking the autism-associated gene Magel2 fail to react to cool sensory stimuli, while autonomic thermoregulatory function is active. This neonatal deficit was mimicked in control neonates by chemogenetic inactivation of oxytocin neurons. Importantly, intranasal administration of oxytocin was able to rescue the phenotype and brain Erk signaling impairment in mutants. This preclinical study establishes for the first-time early life impairments in thermosensory integration and shows the therapeutic potential benefits of intranasal oxytocin treatment on neonatal atypical sensory reactivity.

neuroscience↗

bioRxiv2019

Impaired KCC2 phosphorylation leads to neuronal network dysfunction and neurodevelopmental pathogenesis.

KCC2 is a vital neuronal K+/Cl- co-transporter that is implicated in the etiology of numerous neurological diseases. It is subject to developmental dephosphorylation at threonine 906 and 1007, the functional importance of which remains unclear. We engineered mice with heterozygous phospho-mimetic mutations T906E and T1007E (KCC2E/+) to prevent the normal developmental dephosphorylation of these sites. Immature (P15) but not juvenile (P30) KCC2E/+ mice exhibited altered GABAergic inhibition, an increased glutamate/GABA synaptic ratio, and higher seizure susceptibility. KCC2E/+ mice also had abnormal ultra-sonic vocalizations at P10-P12 and impaired social behavior at P60. Post-natal bumetanide treatment restored network activity at P15 but not social behavior at P60. Our data show that post-translational KCC2 regulation controls the GABAergic developmental sequence in vivo. The post-translational deregulation of KCC2 could be a risk factor for the emergence of neurological pathology and the presence of depolarizing GABA is not essential for manifestation of behavioral changes.

neuroscience↗