Beyond the HPA axis: Synaptic circuits of PVNCRH neurons in stress-related psychiatric disorders

Chronic psychosocial stress is a major risk factor for anxiety, depression and related disorders, yet a hypothalamic-pituitary-adrenal (HPA) axis centric framework alone is insufficient to explain stress-induced vulnerability and phenotypic heterogeneity. Paraventricular nucleus corticotropin-releasing hormone (PVNCRH) neurons are classically regarded as the neuroendocrine entry point for driving glucocorticoid secretion. However, accumulating evidence indicates that, beyond this endocrine role, they also use fast transmitters and CRH co-transmission to form functional projections to diverse brain regions and pre-sympathetic circuits, thereby regulating stress dimensions that extend beyond HPA axis output, including defensive behaviors, reward and motivation, arousal-sleep regulation, autonomic output and glucose homeostasis. In this review, we integrate anatomical, electrophysiological, and behavioral evidence across representative PVNCRH pathways, compare their stress-related functional specialization and shared mechanisms across synaptic and endocrine timescales, and discuss translational implications for circuit-informed pharmacological and neuromodulatory strategies in stress-related psychiatric disorders.