Reduced response to chronic mild stress in PACAP mutant mice is associated with blunted FosB expression in limbic forebrain and brainstem centers

•Lack of PACAP is associated with reduced HPA axis activity in CVMS.•The FosB expression is blunted in the CeA, dmBST, ovBST, vBST, CA1, pPVN, DR in PACAP KO mice.•CRF neurons in the ovBST and Ucn1 cells of the cpEW do not respond to CVMS in PACAP KO mice.•PACAP KO mice show increased serotonin content in DR neurons.•Lack of PACAP influences the stress response in a brain area in a specific manner.