Biology subjects

Montardy, Q.

Publications and source records attributed to Montardy, Q..

6 recordsLinked to original sources

bioRxiv2021

Dopamine modulates visual threat processing in the superior colliculus via D2 receptors

Dopamine (DA) system is intriguing in the aspect that distinct, typically opposing physiological functions are mediated by D1 dopamine receptors (Drd1) and D2 dopamine receptors (Drd2). Both Drd1+ and Drd2+ neurons were identified in superior colliculus (SC), a visuomotor integration center known for its role in defensive behaviors to visual threats. We hypothesized that Drd1+ and Drd2+ neurons in the SC may play a role in promoting instinctive defensive responses. Optogenetic activation of Drd2+ neurons, but not Drd1+ neurons, in the SC triggered strong defensive behaviors. Chemogenetic inhibition of SC Drd2+ neurons decreased looming-induced defensive behavior, suggesting involvement of SC Drd2+ neurons in defensive responses. To further confirm this functional role of Drd2 receptors, pretreatment with the Drd2+ agonist quinpirole in the SC impaired looming-evoked defensive responses, suggesting an essential role of Drd2 receptors in the regulation of innate defensive behavior. Inputs and outputs of SC Drd2+ neurons were investigated using viral tracing: SC Drd2+ neurons mainly receive moderate inputs from the Locus Coeruleus (LC), whilst we did not find any incoming projections from other dopaminergic structures. Our results suggest a sophisticated regulatory role of DA and its receptor system in innate defensive behavior.

neuroscience↗

bioRxiv2020

Novel Model of Reversible Vestibular Syndrom Induced by Optogenetic Stimulation

Glutamatergic and GABAergic neurons represent the neural components of the medial vestibular nuclei. We assessed the functional role of glutamatergic and GABAergic neuronal pathways arising from the vestibular nuclei (VN) in the maintenance of gait and balance by optogenetically stimulating the VN in VGluT2-cre and GAD2-cre mice. We demonstrate that glutamatergic, but not GABAergic VN neuronal subpopulation is responsible for immediate and strong posturo-locomotor deficits, comparable to unilateral vestibular deafferentation models. During optogenetic stimulation, the support surface dramatically increased in VNVGluT2+ mice, and rapidly fell back to baseline after stimulation, whilst it remained unchanged during similar stimulation of VNGAD2+ mice. This effect persisted when vestibular compensation was removed. Posturo-locomotor alterations evoked in VNVGluT2+ animals were still present immediately after stimulation, while they disappeared 1h later. Overall, these results indicate a fundamental role for VNVGluT2+ neurons in balance and posturo-locomotor functions, but not for VNGAD2+ neurons, in this specific context. This new optogenetic approach will be useful to characterize the role of the different VN neuronal populations involved in vestibular physiology and pathophysiology. HighlightsO_LIFor the first time, Vestibular nuclei were optogenetically stimulated in free-moving animals, to asses for glutamatergic and GABAergic neurons functions in posturo-locomotor behaviors. C_LIO_LIBrief optogenetic activation of VNVGluT2+, but not VNGAD2+, induced immediate and strong postural deficit. C_LIO_LIStimulation of VNVGluT2+ neurons provoked an imbalance with continuous effect on locomotion for a short period of time after stimulation. C_LIO_LIThese results are comparable to the classical vestibular deafferentation models during their peak of deficit, and set optogenetic stimulation as a new model to study vestibular deficits. C_LI

neuroscience↗

bioRxiv2020

Mapping the neural circuitry of predator fear in the nonhuman primate

In rodents, innate and learned fear of predators depends on the medial hypothalamic defensive system, a conserved brain network that lies downstream of the amygdala. However, it remains unknown whether this network is involved in primate fear. Here we demonstrate that visually evoked predator fear recruits a homologous medial hypothalamic defense system in the nonhuman primate

neuroscience↗

bioRxiv2019

Glutamatergic and GABAergic neuronal populations in thedorsolateral Periacqueductual Gray have differentfunctional roles in fear conditioning

It is though that only a subset of brain structures can encode emotional states. This can be investigated though a set of properties, including the ability of neurons to respond to a conditioned stimulus (CS) preceding an aversive unconditioned stimulus (US). The dorsolateral periacqueductal gray (dPAG) is a midbrain structure though to have an essential role in coordinating defensive behaviors in response to aversive stimulation. But its ability of dPAG neurons to encode a CS following fear conditioning as not been sufficiently studied.\n\nHere we used calcium imaging by fiber photometry to record the activity of dPAGVGluT2+ and dPAGGAD2+ neuronal populations during unconditioned and conditioned aversive stimulation. Then, following an unconditioned stimulation we performed a retrieval experiment to quantify memory-like responses of dPAG neurons. This shown that whilst both dPAGVGluT2+ and dPAGGAD2+ neuronal populations respond to direct US stimulation, and to CS stimulation during conditioning, only the dPAGVGluT2+ population persisted in responding to the CS stimulation during retrieval. Finally, to better understand dPAGVGluT2+ and dPAGGAD2+ connectivity patterns, we performed a cell specific monosynaptic retrograde rabies virus tracing experiment. This revealed that different patterns of fibers projects to dPAGVGluT2+ and dPAGGAD2+, further complementing our recording showing divergences between PAGVGluT2+ and dPAGGAD2+ populations.

neuroscience↗

bioRxiv2018

A VTA GABAergic neural circuit mediates visually evoked innate defensive responses

Innate defensive responses are essential for animal survival and are conserved across species. The ventral tegmental area (VTA) plays important roles in learned appetitive and aversive behaviors, but whether it plays a role in mediating or modulating innate defensive responses is currently unknown. We report that GABAergic neurons in the mouse VTA (VTAGABA+) are preferentially activated compared to VTA dopaminergic (VTADA+) neurons when a threatening visual stimulus evokes innate defensive behavior. Functional manipulation of these neurons showed that activation of VTAGABA+ neurons is indispensable for looming-evoked defensive flight behavior and photoactivation of these neurons is sufficient for looming-evoked defensive-like flight behavior, whereas no such role can be attributed for VTADA+ neurons. Viral tracing and in vivo and in vitro electrophysiological recordings showed that VTAGABA+ neurons receive direct excitatory inputs from the superior colliculus (SC). Furthermore, we showed that glutamatergic SC-VTA projections synapse onto VTAGABA+ neurons that project to the central nucleus of the amygdala (CeA) and that the CeA is involved in mediating the defensive behavior. Our findings demonstrate that visual information about aerial threats access to the VTAGABA+ neurons mediating innate behavioral responses, suggesting a more general role for the VTA.

neuroscience↗

bioRxiv2018

Characterization of glutamatergic VTA neural population responses to aversive and rewarding conditioning in freely-moving mice

The Ventral Tegmental Area (VTA) is a midbrain structure known to integrate aversive and rewarding stimuli, a function involving VTA Dopaminergic and GABAergic neurons. VTA also contains a less known population: glutamatergic (VGluT2) neurons. Direct activation of VGluT2 soma evokes rewarding behaviors, while stimulation of their axonal projections to the Nucleus Accumbens (NAc) and the Lateral Habenula (LHb) evokes aversive behaviors. Here, a systematic investigation of the VTAVGluT2+ population response to aversive or rewarding conditioning facilitated our understanding these conflicting properties. We recorded calcium signals from VTA glutamatergic population neurons using fiber photometry in VGluT2-cre mice to investigate how the VTA glutamatergic neuronal population was recruited by aversive and rewarding stimulation, both during unconditioned and conditioned protocols. Our results revealed that, as a population, VTAVGluT2+ neurons responded similarly to unconditioned-aversive and unconditioned-rewarding stimulation. During aversive and rewarding conditioning, the CS-evoked responses gradually increased across trials whilst the US-evoked response remained stable. Retrieval 24 h after conditioning, during which mice received only CS presentation, resulted in VTAVGluT2+ neurons strongly responding to CS presentation and to the expected-US but only for aversive conditioning. The inputs and outputs of VTAVGluT2+ neurons were then investigated using Cholera Toxin B (CTB) and rabies virus, and we propose based on all results that VTAVGluT2+ neurons specialized function may be partially due to their connectivity.

neuroscience↗