Central amygdala CRF+ neurons tune defensive state stability during threat

The central amygdala (CeA) is critical for mediating behavioral responses to threat,^1,2 including the coordination of competing freezing and mobile responses through distinct cell types.^3,4,5,6 Defensive behavior must remain flexible as threat contingencies change,^7,8 yet the circuit mechanisms that regulate how threat is translated into appropriate defensive states remain unclear. Using a dual-threat conditioning paradigm, we found that divergence from an immobility-dominant passive phenotype during a temporally immediate threat (delay conditioned stimulus [CS]) toward a more active phenotype during a variable-trace threat (variable trace CS; vTrace) emerged specifically through increased disengagement from immobility. Chronic unpredictable stress (CUS) disrupted this transition-level phenotype in males, thereby promoting immobility persistence that generalized during the trace threat. To identify the circuit mechanisms underlying these effects, we manipulated CeA neurons expressing corticotropin-releasing factor (CeA CRF+) during threat recall using chemogenetics and blocked CRFR1 signaling via systemic administration of the antagonist antalarmin. Silencing CeA CRF+ neurons and CRFR1 antagonism reduced transitions out of immobility without impairing cue discrimination, thus phenocopying the transition-level deficit observed in CUS males. These findings suggest that stress-induced behavioral rigidity, particularly under temporal uncertainty of threat, may arise from impaired CRF-dependent destabilization of passive defensive states. Together, our findings indicate that CeA CRF+ neurons and CRFR1 signaling regulate threat responding by facilitating the transitions out of immobility during threat evaluation. This work identifies CRF signaling as a mechanism that enables defensive responding to adjust to temporal threat contingencies, which may be disrupted in fear-related pathology.