Chronic stress alters the E/I balance of pyramidal neurons in the infralimbic and Prelimbic cortices

The medial prefrontal cortex (mPFC) is a key brain region involved in controlling working memory, executive function, and self-regulatory behaviours, and its malfunction is a hallmark of several neuropsychiatric disorders such as schizophrenia, depression, and post-traumatic stress disorder. One of the main risk factors for the development of mental illness is chronic stress (CS). Despite some evidence pointing to possible excitation-inhibition (E/I) imbalances caused by CS, the precise mechanism by which CS triggers mPFC dysfunction is not fully understood. Here, using neuroproteomics analysis and whole-cell patch-clamp recordings, we investigated the functional changes in E/I ratio and synaptic drive onto pyramidal neurons and parvalbumin interneurons (PV) in the prelimbic (PL) and infralimbic (IL) cortices, following exposure to 21 days of chronic unpredictable stress. We demonstrate that CS impacts PL- versus IL-pyramidal neurons differently, driving a common decrease in E/I ratio without affecting PV interneurons. Our work brings insightful information and corroborates the hypothesis of stress-induced hypofunction of the mPFC.