Apelin-13 reverses memory impairment and depression-like behavior in chronic social defeat stressed rats

The apelin/APJ signaling is composed of the short peptide apelin usually including apelin-13, apelin-17 and apelin-36, and its receptor APJ. This signaling is abundantly expressed in limbic structures such as the hippocampus, suggesting a potential role in stress response and learning and memory. We recently reported that apelin-13 reverses acute stress-induced memory impairment and depression-like behavior in rats. Here, we further investigate whether apelin-13 reverses memory impairment and depression-like behavior in chronic stressed rats. Rats were subjected to chronic social defeat stress (CSDS), and received intracerebroventricular infusion of apelin-13 for one week after stress withdrawal. Behavioral test battery was performed to assess memory performance and depression-like behavior. Results showed that apelin-13 reversed CSDS-induced decrease in the alternation ratio and discrimination index in the Y-maze and novel object recognition tests, respectively. Apelin-13 also reversed CSDS-induced social avoidance in the social interaction test, and behavioral despair in the forced swimming and tail suspension tests. Additionally, apelin-13 did not influence locomotor activity in the open field test. These observations suggest that apelin-13 reverses memory impairment and depression-like behavior in chronic stressed rats.