Mineralocorticoid receptor signaling in GABAergic neurons regulates stress-induced cognitive flexibility.

The mineralocorticoid receptor (MR) plays a pivotal role in modulating the neuroendocrine stress response and cognitive function. While recent evidence highlights the importance of MRs in glutamatergic neurons in regulating anxiety-like behavior, the specific contribution of MRs within inhibitory networks remains incompletely understood. To address this gap, we generated a mouse model with targeted ablation of MR in forebrain GABAergic neurons (MRDlx). Comprehensive behavioral profiling revealed a profound, state-dependent cognitive phenotype in male MRDlx mice. Under non-stressful baseline conditions, these mice exhibited impaired object recognition memory, while under aversive learning paradigms, such as the Morris water maze and fear conditioning, they displayed enhanced spatial and contextual memory. Furthermore, male MRDlx mice demonstrated significant behavioral lack of adaptation to 21 days of chronic social defeat stress (CSDS). Notably, these changes were highly sex-influenced, as female MRDlx mice did not exhibit the same baseline cognitive deficits or subsequent stress resistance. Mechanistically, in vitro hippocampal electrophysiological recordings from male mice showed that acute corticosterone (CORT) application, which typically suppresses long-term potentiation (LTP), failed to impair LTP in MRDlx slices, indicating a marked resistance to CORT-induced suppression. Together, our findings suggest that MRs in GABAergic neurons normally function as critical constraints on excitatory synaptic plasticity during high-stress states. Ablating this regulatory mechanism confers robust behavioral and synaptic stress resistance, underscoring that adaptive stress responses rely on a finely tuned, cell-type-specific balance of corticosteroid signaling within limbic microcircuits.