¹Jichi Medical University, School of Medicine, Division of Histology and Cell Biology, Shimotsuke, Japan, ²Kobe University, Graduate School of Medicine, Division of Pharmacology, Kobe, Japan, ³Sumitomo Pharma, Research and Development Division, Osaka, Japan, ⁴Kyoto University, Graduate School of Medicine, Department of Pharmacology, Kyoto, Japan, ⁵Kazusa DNA Research Institute, Department of Applied Genomics, Kisarazu, Japan, ⁶National Institute for Physiological Sciences, Division of Ultrastructural Research, Okazaki, Japan, ⁷Kobe University, Graduate School of Science, Technology and Innovation, Laboratory for Biomodulation, Kobe, Japan, ⁸University of Osaka, Graduate School of Engineering, Department of Biotechnology, Osaka, Japan, ⁹Kansai Medical University, Institute of Biomedical Science, Department of Molecular Genetics, Hirakata, Japan, ¹⁰RIKEN Center for Biosystems Dynamics Research, Laboratory for Molecular and Cellular Dynamics, Kobe, Japan, ¹¹Keio University, Human Biology-Microbiome-Quantum Research Center, Tsuruoka, Japan, ¹²Institute of Science Tokyo, Graduate School of Medical and Dental Sciences, Department of Pharmacology, Tokyo, Japan

Background: Stress-related psychiatric disorders, including depression, are closely associated with alterations in synaptic structure and function in higher-order cortical regions. Accumulating evidence suggests that mitochondrial dysfunction contributes to stress-induced synaptic pathology. However, how chronic stress affects metabolic pathways at synapses, and how such alterations translate into behavioral abnormalities, remain unclear.

Aims & Objectives: Given the central role of energy metabolism in synaptic maintenance and plasticity, we examined the impact of chronic social stress on metabolic regulation at prefrontal cortical synapses and its functional implications.

Method: Male C57BL/6 mice were subjected to chronic social defeat stress. After chronic stress exposure, animals were categorized as stress-susceptible or resilient based on social interaction behavior. Synaptic structure and mitochondrial ultrastructure in the medial prefrontal cortex were analyzed using three-dimensional electron microscopy, expansion microscopy, and confocal imaging. Synaptic mitochondrial function was assessed using biochemical and respiratory assays. Comprehensive proteomic and metabolomic analyses, including mass spectrometry imaging, were employed to characterize stress-induced metabolic alterations. Neuronal activity was monitored by in vivo two-photon calcium imaging. To evaluate functional relevance, metabolic pathways were experimentally modulated in prefrontal neurons and their effects on synaptic integrity, neuronal activity, and behavior were assessed.

Results: Chronic social stress selectively reduced the size of mitochondria-containing synapses and induced marked abnormalities in synaptic mitochondrial morphology and function. Proteomic and metabolomic profiling revealed pronounced stress-dependent alterations in central metabolic pathways, particularly those associated with mitochondrial energy production. Spatial metabolomic analysis demonstrated region-specific metabolic dysregulation in the medial prefrontal cortex. Importantly, targeted modulation of central metabolic processes restored synaptic structure, normalized neuronal activity, and alleviated depression-related behaviors in stressed mice.

Discussion & Conclusions: These findings demonstrate that chronic stress disrupts central energy metabolism at prefrontal cortical synapses, driving to synaptic pathology and behavioral vulnerability. Our results highlight synaptic metabolic pathways as promising pharmacological targets for the treatment of stress-related psychiatric disorders.