Biology subjects

Baufreton, J.

Publications and source records attributed to Baufreton, J..

7 recordsLinked to original sources

bioRxiv2026

Neurospheres from primary rodent brain cells to probe the 3D organization and function of synapses

To improve our understanding of synapse assembly, there is a need for robust, easy-to-use, and physiologically relevant in-vitro models allowing the controllable formation of neuronal contacts in a reasonable time, whose structure and function can be investigated using advanced microscopy. To address this challenge, we engineered 3D cultures from rodent dissociated hippocampal cells, that spontaneously assemble in low attachment U-bottom wells into compact spheroids of reproducible dimensions (100-300 microns), determined by the number of seeded cells. These neurospheres contain a mix of neurons and glial cells and grow over time in culture, through the combination of cell proliferation and neurite extension. Neurospheres were immunostained in fluid phase, and/or sparsely electroporated for the multi-color visualization of synaptic proteins. Neurons extend an elaborate network of axons and dendrites, forming within 2 weeks numerous excitatory and inhibitory synapses identified at the structural level by confocal and electron microscopy, and at the functional level by electrophysiology. Periodic calcium oscillations throughout neurospheres further highlight network activity. Finally, we demonstrate the potential of neurospheres to study synaptogenesis by modulating and visualizing the adhesion protein neuroligin-1. Overall, neurospheres represent a standardized and cost-effective system to study synapse structure and function at high resolution in 3D, that should be quite appealing to the cellular neurobiology community.

neuroscience↗

bioRxiv2025

A subset of dorsal raphe dopamine neurons is critical for survival-oriented vigilance.

Defensive behaviors are essential for survival, with risk assessment enabling organisms to evaluate and respond to potential threats. The dorsal raphe nucleus (DRN), a key neuromodulatory center, is crucial for encoding motivational salience and regulating arousal and sleep-wake states through its diverse neuronal populations, including dopaminergic neurons (DRNDA). While the roles of DRNDA neurons have been studied, their specific contributions to threat evaluation are less understood. Recent research identifies a distinct subset of DRNDA neurons that express vasoactive intestinal peptide (VIP) and project to the central amygdala (CeA) and the oval nucleus of the bed nucleus of the stria terminalis (ovBNST). Together, these two regions comprise the central extended amygdala, a key network regulating adaptive responses to threats. We hypothesized that distinct DRNDA subpopulations exert diverging effects on sleep-wake regulation and that DRNVIP neurons play a pivotal role in coordinating activity between the CeA and ovBNST, thereby influencing risk assessment and defensive response. To test this hypothesis, we used a combination of in situ hybridization, immunochemistry, whole-brain mapping, electrophysiology, and cell-specific genetic tools in mice and non-human primates. Our findings reveal that DRNVIP neurons form a key DRNDA neuronal subset, uniquely positioned to regulate the central extended amygdala through a feedback loop. These neurons receive inputs from Protein Kinase C delta (PKC-{delta}) neurons in the ovBNST and CeA and send glutamate-releasing projections back to these regions, modulating PKC-{delta} neuron excitability. Selective ablation of DRNVIP neurons increases activity in both the BNST and CeA, disrupting active-phase sleep architecture and impairing risk assessment and defensive behaviors. Together, these findings suggest DRNVIP neurons control specific phases of sleep and orchestrate the central extended amygdalas role in risk assessment and defensive responses. HIGHLIGHTSO_LIDRNVIP neurons form a subset of DRNDA neurons in mice and non-human primates. C_LIO_LIDRNVIP receive inputs from Protein Kinase C delta (PKC-{delta}) neurons in the ovBNST and CeA and project back to both. C_LIO_LIBy releasing glutamate, DRNVIP neurons regulate PKC-{delta} neuron excitability in the ovBNST and CeA. C_LIO_LIAblating DRNVIP neurons increases BNST and CeA activity, disrupts active-phase sleep architecture, and impairs threat responses. C_LI IN BRIEFDRNVIP neurons, a key subset of DRNDA neurons in mice and primates, are strategically positioned to influence the central extended amygdala via feedback loops. They regulate PKC-{delta} neuron excitability in the ovBNST and CeA through glutamate release, with their ablation heightening activity in these regions and altering active-phase sleep architecture, risk assessment and defensive behaviors.

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bioRxiv2024

Disruption of the CRF1 receptor eliminates morphine-induced sociability deficits and firing of oxytocinergic neurons in male mice

Substance-induced social behavior deficits dramatically worsen the clinical outcome of substance use disorders; yet, the underlying mechanisms remain poorly understood. Herein, we investigated the role for the corticotropin-releasing factor receptor 1 (CRF1) in the acute sociability deficits induced by morphine and the related activity of oxytocin (OXY)-and arginine-vasopressin (AVP)-expressing neurons of the paraventricular nucleus of the hypothalamus (PVN). For this purpose, we used both the CRF1 receptor-preferring antagonist compound antalarmin and the genetic mouse model of CRF1 receptor-deficiency. Antalarmin completely abolished sociability deficits induced by morphine in male, but not in female, C57BL/6J mice. Accordingly, genetic CRF1 receptor-deficiency eliminated morphine-induced sociability deficits in male mice. Ex vivo electrophysiology studies showed that antalarmin also eliminated morphine-induced firing of PVN neurons in male, but not in female, C57BL/6J mice. Likewise, genetic CRF1 receptor-deficiency reduced morphine-induced firing of PVN neurons in a CRF1 gene expression-dependent manner. The electrophysiology results consistently mirrored the behavioral results, indicating a link between morphine-induced PVN activity and sociability deficits. Interestingly, in male mice antalarmin abolished morphine-induced firing in neurons co-expressing OXY and AVP, but not in neurons expressing only AVP. In contrast, in female mice antalarmin did not affect morphine-induced firing of neurons co-expressing OXY and AVP or only OXY, indicating a selective sex-specific role for the CRF1 receptor in opiate-induced PVN OXY activity. The present findings demonstrate a major, sex-linked, role for the CRF1 receptor in sociability deficits and related brain alterations induced by morphine, suggesting new therapeutic strategy for opiate use disorders.

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bioRxiv2023

Age-dependent modulation of the excitability of layer V pyramidal neurons by dopamine D1 receptors in mices primary motor cortex

The primary motor cortex (M1) receives dopaminergic (DAergic) projections from the midbrain which play a key role in modulating motor and cognitive processes, such as motor skill learning. However, little is known at the level of individual neurons about how dopamine (DA) and its receptors modulate the intrinsic properties of the different neuronal subpopulations in M1 and if this modulation depends on age. Using immunohistochemistry, we first mapped the cells expressing the DA D1 receptor across the different layers in M1, and quantified the number of pyramidal neurons (PNs) expressing the D1 receptor in the different layers, in young and adult mice. This work reveals that the spatial distribution and the molecular profile of D1 receptor-expressing neurons across M1 layers do not change with age. Then, combining whole-cell patch-clamp recordings and pharmacology, we explored ex vivo in young and adult mice the impact of activation or blockade of D1 receptors on PN intrinsic properties and identified a distinct modulation of intrinsic electrical properties of layer V PNs by D1 receptors depending on the age of the animal. HighlightsO_LIThe laminar distribution in M1 of cells expressing the dopamine D1 receptor is similar in young and adult mice C_LIO_LIMost of D1R-expressing cells in M1 also express Satb2 C_LIO_LID1R activation increases M1 layer V pyramidal neurons excitability both in young and adult mice C_LIO_LIThe effect of D1R blockade on M1 layer V pyramidal neurons excitability differs between young and adult mice C_LI

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bioRxiv2022

Encoding social preference by interhemispheric neurons in the Insula

The Insula is a multisensory relay that participates in socio-emotional processing through multiple projections to sensory, cognitive, emotional, and motivational regions. Interestingly, the Insula interhemispheric projection to the contralateral Insula is a strong but understudied projection. Using cutting-edge neuroanatomy, ex vivo and in vivo electrophysiology associated with specific circuit manipulation, we unraveled the nature and role of Insula interhemispheric communication in social and anxiety processing in mice. In this study, we 1) characterized the anatomical and molecular profile of the interhemispheric neurons of the Insula, 2) highlighted that stimulation of this neuronal subpopulation triggers excitation in the Insula interhemispheric circuit 3) uncovered their engagement in social processing. In conclusion, this study demonstrates that interhemispheric neurons of the Insula constitute a unique class of Insula neurons and proposes new meaningful insights into the neuronal mechanisms underlying social behavior.

neuroscience↗

bioRxiv2020

A disynaptic circuit in the globus pallidus controls locomotion inhibition

Basal ganglia (BG) inhibit movement through two independent pathways, the indirect- and the hyperdirect-pathways. The globus pallidus (GP) has always been viewed as a simple relay within these two pathways, but its importance has changed drastically with the discovery of two functionally-distinct cell types, namely the prototypic and the arkypallidal neurons. Classic BG models suggest that all GP neurons receive GABAergic inputs from striato-pallidal indirect spiny projection neurons and glutamatergic inputs from subthalamic neurons. However, whether this synaptic connectivity scheme applies to both GP cell-types is currently unknown. Here, we optogenetically dissect the input organization of prototypic and arkypallidal neurons and further define the circuit mechanism underlying action inhibition in BG. Our results highlight that an increased activity of arkypallidal neurons is required to inhibit locomotion. Finally, this work supports the view that arkypallidal neurons are part of a novel disynaptic feedback loop that broadcast inhibitory control on movement execution.

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bioRxiv2019

Dopamine D2 receptors modulate intrinsic properties and synaptic transmission of parvalbumin interneurons in the mouse primary motor cortex

Dopamine (DA) plays a crucial role in the control of motor and higher cognitive functions such as learning, working memory and decision making. The primary motor cortex (M1), which is essential for motor control and the acquisition of motor skills, receives dopaminergic inputs in its superficial and deep layers from the midbrain. However, the precise action of DA and DA receptor subtypes on the cortical microcircuits of M1 remains poorly understood. The aim of this work was to investigate how DA, through the activation of D2 receptors (D2R), modulates the cellular and synaptic activity of M1 parvalbumin-expressing interneurons (PVINs) which are crucial to regulate the spike output of pyramidal neurons (PNs). By combining immunofluorescence, ex vivo electrophysiology, pharmacology and optogenetics approaches, we show that D2R activation increases neuronal excitability of PVINs and GABAergic synaptic transmission between PVINs and PNs in layer V of M1. Our data reveal a mechanism through which cortical DA modulates M1 microcircuitry and might participate in the acquisition of motor skills.\n\nSignificance StatementPrimary motor cortex (M1), which is a region essential for motor control and the acquisition of motor skills, receives dopaminergic inputs from the midbrain. However, precise action of dopamine and its receptor subtypes on specific cell types in M1 remained poorly understood. Here, we demonstrate in M1 that dopamine D2 receptors (D2R) are present in parvalbumin interneurons (PVINs) and their activation increases the excitability of the PVINs, which are crucial to regulate the spike output of pyramidal neurons (PNs). Moreover the activation of the D2R facilitates the GABAergic synaptic transmission of those PVINs on layer V PNs. These results highlight how cortical dopamine modulates the functioning of M1 microcircuit which activity is disturbed in hypo- and hyperdopaminergic states.

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