CHRONIC STRESS REPROGRAMS SYNAPTIC AND TRANSCRIPTIONAL SIGNATURES OF THE MPFC-VTA CIRCUITRY TO IMPAIR COGNITION

Cortical dysregulation of subcortical circuits is a key mechanism underlying mood and cognitive disorders. The medial prefrontal cortex (mPFC) exerts top-down control over the ventral tegmental area (VTA), a critical node of the mesocorticolimbic network regulating motivation and cognitive control. Previous work from our group showed that chronic stress induces structural and functional alterations in mPFC neurons projecting to the VTA. However, how these changes translate into downstream synaptic and transcriptional dysregulation within the VTA and impair cognition remains unclear. We first assessed circuit engagement using pathway-specific fiber photometry. Calcium imaging of mPFC-VTA neurons during a working memory task revealed time-locked elevations preceding decision points, indicating recruitment of this pathway during cognitive processing. To identify the synaptic basis of this activity, we combined optogenetics with ex vivo electrophysiology. Optical stimulation of mPFC terminals in the VTA induced short-term facilitation of excitatory transmission onto dopaminergic neurons, relying on presynaptic calcium-interacting proteins. Stunningly, this plasticity was strongly impaired following chronic stress. To uncover the molecular substrate of this facilitation
and how stress reshapes these synapses, we performed a pathway-specific RNA sequencing of mPFC neurons projecting to the VTA. In females, chronic stress profoundly downregulated Calhm1, a gene encoding a Ca²⁺ homeostatic channel. CRISPR-mediated suppression of Calhm1 in naïve females recapitulated stress-induced synaptic deficits and impaired working memory and coping behavior. Together, these findings identify a stress-sensitive synaptic and transcriptional program at mPFC–VTA connections that supports cognitive function and highlights circuit-specific calcium regulation as a potential target for restoring cognition after stress.