Enhanced Adenosine A1 Receptor and Homer1a Expression in Hippocampus Modulates the Resilience to Stress-Induced Depression-Like Behavior.

Resilience to stress is critical for the development of depression. Enhanced adenosine A(1) receptor (AIR) signaling mediates the antidepressant effects of acute sleep deprivation (SD). However, chronic SD causes long-lasting upregulation of brain A(1)R and increases the risk of depression. To investigate the effects of A(1)R on mood, we utilized two transgenic mouse lines with inducible A(1)R overexpression in forebrain neurons. These two lines have identical levels of A(1)R increase in the cortex, but differ in the transgenic A(1)R expression in the hippocampus. Switching on the transgene promotes robust antidepressant and anxiolytic effects in both lines. The mice of the line without transgenic A(1)R overexpression in the hippocampus (A1Hipp-) show very strong resistance towards development of stress-induced chronic depression-like behavior. In contrast, the mice of the line in which A(1)R upregulation extends to the hippocampus (A1Hipp +), exhibit decreased resilience to depression as compared to A1Hipp-. Similarly, automatic analysis of reward behavior of the two lines reveals that depression resistant A1Hipp-transgenic mice exhibit high sucrose preference, while mice of the vulnerable A1Hipp + line developed stress-induced anhedonic phenotype. The A1Hipp + mice have increased Homer1a expression in hippocampus, correlating with impaired long-term potentiation in the CA1 region, mimicking the stressed mice. Furthermore, virus-mediated overexpression of Homer1a in the hippocampus decreases stress resilience. Taken together our data indicate for first time that increased expression of AIR and Homer1a in the hippocampus modulates the resilience to stress-induced depression and thus might potentially mediate the detrimental effects of chronic sleep restriction on mood.