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.