Blockade of CRF1 and CCK2 receptors attenuated the elevated anxiety-like behavior induced by immobilization stress.

Two highly co-localized neurotransmitters: corticotropin-releasing factor (CRF) and cholecystokinin (CCK), have been implicated in the development of stress-related anxiety disorders. This study was designed to examine the role of CRF1 and CCK2 receptors on the anxiety-like behavior induced by immobilization stress. Our results showed that 30-min immobilization enhanced the anxiety-like behavior in C57BL/6J mice examined in the elevated plus maze (EPM). The combined pretreatment of CR2945 (a CCK2 receptor antagonist) and antalarmin (a CRF1 receptor antagonist) fully blocked this elevated anxiety-like behavior, while the application of CR2945 or antalarmin alone showed only partial effects. The increased expression of CRF1 and CCK2 receptors at protein levels in three anxiety-related brain regions: cortex, hippocampus and hypothalamus, was detected by Western blot. The increased mRNA expression of CCK, CRF, CCK2 and CRF1 receptors was also examined by real-time RT-PCR. Our study demonstrated that the blockade of CRF1 and CCK2 receptors attenuated the elevated anxiety-like behavior induced by immobilization stress, suggestive of the CRF and CCK systems contributing to the development of stress-related anxiety behavior.