Biology subjects

Proulx, C. D.

Publications and source records attributed to Proulx, C. D..

6 recordsLinked to original sources

bioRxiv2026

Recurrent neuronal loops between medial prefrontal cortex and ventral tegmental area display sex-specific spatial reorganization in response to stress

The medial prefrontal cortex (mPFC) and ventral tegmental area (VTA) form a highly interconnected circuit involved in emotional regulation, stress reactivity, and cognitive processing. While prior research has established the anatomical and functional interactions between these regions, the precise organization and molecular identity of VTA neurons involved in unidirectional and bidirectional mPFC connectivity remains poorly defined, particularly under stress. We combined dual anterograde and retrograde viral tracing in male and female mice to label VTA neurons according to their connectivity with the mPFC. This approach identified three distinct subpopulations including mPFC-projecting, mPFC-receiving, and bidirectionally-connected neurons which accounted for nearly half of the labelled VTA population. Each group displayed molecular heterogeneity, with most cells expressing dopaminergic (TH) and glutamatergic (VGLUT2) transcripts rather than single dopaminergic or GABAergic (GAD1) markers. Acute and chronic stress exposure revealed sex- and circuit-specific patterns of c-Fos activation. In males, acute and chronic stress generated opposing rostrocaudally organized activation profiles, whereas females showed a more uniform increase in activity. Spatial clustering analyses further revealed that stress induces distinct hotspot organization within the VTA, with chronic stress promoting cohesive hotspot organization and consistent local enrichment of bidirectionally connected neurons despite a limited global activation. Together, these findings uncover a molecularly diverse mPFC-VTA circuitry with bidirectional connectivity that undergoes sex-dependent spatial and functional rearrangement under stress, providing new insights on circuit-level mechanisms of stress-related disorders.

neuroscience↗

bioRxiv2026

Lateral hypothalamic input engages a disinhibitory microcircuit in the dorsal raphe to promote behavior activation

Behavioral activation involves coordination between hypothalamic and brainstem systems that regulate movement and internal state, but the circuit logic underlying this interaction remains poorly defined. The dorsal raphe nucleus (DRN), a major serotonergic hub, integrates diverse inputs to influence behavioral inhibition and activation, yet how hypothalamic signals shape its activity is unclear. Here, we identify a disinhibitory pathway through which the lateral hypothalamus (LHA) promotes behavioral activation via DRN. Using intersectional viral tracing, electrophysiology, and single-nucleus RNA sequencing, we show that LHA inputs preferentially target GABAergic DRN neurons that locally inhibit 5-HT neurons. Silencing these DRN neurons innervated by LHA increased locomotor and repetitive behaviors, decreased local inhibition, and enhanced cFos activity in serotonergic neurons, consistent with circuit-level disinhibition. Molecular profiling revealed distinct transmitter identities and transcriptional signatures of LHA-targeted versus LHA-projecting DRN populations. Together, these findings delineate a hypothalamic-raphe circuit that transforms hypothalamic drive into serotonergic activation, revealing a mechanism by which the lateral hypothalamus promotes behavioral activation through local inhibitory control. HIGHLIGHTSO_LILHA inputs preferentially target non-serotonergic, transcriptionally distinct DRN neurons C_LIO_LILHA-innervated DRN neurons form extensive local inhibition C_LIO_LISilencing LHA-innervated DRN neurons reduced local inhibitory tone and activate serotonin neurons C_LIO_LIDisrupting this circuit drives behavioral activation with repetitive motor pattern, not anxiety C_LI

neuroscience↗

bioRxiv2026

CRISPR/CAS9-MEDIATED LOSS OF VESICULAR GLUTAMATE TRANSPORTER IN SEROTONIN NEURONS OF THE DORSAL RAPHE NUCLEUS LEADS TO SYNAPTIC CHANGES AND ANXIETY-LIKE BEHAVIORS

Vesicular glutamate transporter 3 (VGluT3) is expressed in a large subset of serotonin (5-HT) neurons of the dorsal raphe nucleus (DRN), suggesting a potential for glutamate co-transmission. Although VGluT3 has been implicated in the physiology of several non-glutamatergic neuronal populations, its specific role in the organization and function of 5-HT axons remains unclear. Here, we used CRISPR-Cas9 mediated knockdown and viral overexpression of VGluT3 in DRN 5-HT neurons of adult mice to assess its contribution to synaptic architecture in the lateral hypothalamus (LHA) and to 5-HT-related behaviors. VGluT3 depletion did not significantly alter synaptic incidence or organization of 5-HT DRN terminals in the LHA. In contrast, VGluT3 overexpression increased the proportion of asymmetric synapses without changing the overall synaptic incidence. In behavioral assays, VGluT3 depletion impaired motor coordination and increased anxiety-like, repetitive, and social behavior, whereas VGluT3 overexpression selectively reduced repetitive behavior. Basal locomotion and depressive-like behaviors were unchanged by either manipulation. Together, these findings indicate that VGluT3 modulates both the structural organization and behavioral output of DRN 5-HT neurons, supporting a modulatory role for VGluT3-dependent signaling within 5-HT circuits.

neuroscience↗

bioRxiv2025

The Lateral Habenula to Ventral Tegmental Area Pathway is Required for Aversive Learning and Defensive Behaviors

The lateral habenula (LHb) provides aversive signals to the ventral tegmental area (VTA), but its contribution to learning and behavior remains poorly understood. Using a retrograde viral strategy, we targeted VTA-projecting LHb neurons and monitored calcium activity during active avoidance training. These neurons were activated by aversive stimuli and predictive cues as animals acquired avoidance responses and showed increased activity at movement onset during the tail suspension test (TST). Silencing LHb[->]VTA transmission impaired avoidance learning, prolonged escape latency, and reduced the persistence and vigor of active coping in the TST, without affecting baseline locomotion. Anatomical and ex vivo electrophysiology revealed that LHb terminals innervate both dopaminergic (TH) and non-dopaminergic (TH-) VTA neurons, exhibiting session-specific synaptic adaptations during avoidance learning. Together, these findings identify the LHb[->]VTA pathway as a source of aversive predicting signals required for the acquisition of avoidance behavior and the persistence of active coping in aversive context. HighlightsO_LILHb[->]VTA neurons are required for aversive learning and adaptive avoidance C_LIO_LIThese neurons respond to aversive stimuli, predictive cues, and movement onset C_LIO_LISilencing the pathway impairs avoidance learning and reduces active coping in aversive contexts C_LIO_LILHb[->]VTA inputs innervate DA and non-DA neurons and undergo learning-related plasticity C_LI

neuroscience↗

bioRxiv2024

Transcriptional profiling of the cortico-accumbal pathway reveals sex-specific alterations underlying stress susceptibility

Anxiety and depressive disorders, including major depressive disorder (MDD), affect millions of people every year, imposing significant socio-economic burdens. In this scenario, current treatments for MDD show limited efficacy, highlighting the need to better understand its molecular mechanisms. The medial prefrontal cortex (mPFC) has been identified as a critical brain region in MDD pathology, displaying altered activity and morphology. This study targets the mPFC-to-nucleus accumbens (NAc) pathway, which is implicated in the regulation of emotional behavior. We used a pathway-specific approach to uncover transcriptional profiles in mPFC neurons projecting to the NAc in stressed male and female mice. Using the RiboTag technique and RNA sequencing, we identified sex-specific gene expression changes, revealing potential roles in stress susceptibility. Differential expression and weighted gene co-expression network analyses revealed distinct transcriptional responses to chronic stress in males and females. Key findings include the identification of the X-linked lymphocyte-regulated 4B (Xlr4b) gene, within a highly relevant gene module, as a stress susceptibility driver in males. By experimentally overexpressing the Xlr4b gene, we characterized its crucial role in regulating neuronal firing and influencing arborization patterns to promote anxiety-like behavior in a sex-specific fashion. These findings suggest that chronic stress induces unique and shared transcriptional alterations in mPFC neurons projecting to the NAc. Some of these alterations change the morphological and functional properties of neuronal pathways ultimately contributing to the differential manifestation of anxiety-like and depressive-like behaviors in male and female mice.

neuroscience↗

bioRxiv2020

Chronic stress induces sex-specific functional and morphological alterations in cortico-accumbal and cortico-tegmental pathways.

BackgroundThe medial prefrontal cortex (mPFC) is part of a complex circuit controlling stress responses by sending projections to different limbic structures including the nucleus accumbens (NAc) and ventral tegmental area (VTA). However, the impact of chronic stress on NAc- and VTA-projecting mPFC neurons is still unknown and the distinct contribution of these pathways to stress responses in males and females is unclear. MethodsBehavioral stress responses were induced by 21 days of chronic variable stress (CVS) in male and female C57BL6 mice. An inter-sectional viral approach was used to label both pathways and assess the functional, morphological, and transcriptional adaptations in NAc- and VTA-projecting mPFC neurons in stressed males and females. Using chemogenetic approaches, we modified neuronal activity of NAc-projecting mPFC neurons to decipher their contribution to stress phenotypes. ResultsCVS induced depressive-like behaviors in males and females. NAc- and VTA-projecting mPFC neurons exhibited sex-specific functional, morphological, and transcriptional alterations. The functional changes were more severe in females in NAc-projecting mPFC neurons while males exhibited more drastic reductions in dendritic complexity in VTA-projecting mPFC neurons after CVS. Finally, chemogenetic overactivation of the cortico-accumbal pathway triggered anxiety and behavioral despair in both sexes while its inhibition rescued the phenotype only in females. ConclusionsOur results suggest that by changing the activity of transcriptional programs controlling neuronal plasticity, CVS interferes with the morphological and synaptic properties of the cortico-accumbal and tegmental pathways differently in males and females contributing to the expression of anxiety and depressive-like behaviors distinctly in a sex-specific fashion.

neuroscience↗