Clock genes Period1 and Period2 in the hippocampal CA1 mediate depression-like behaviors and rapid antidepressant response

Accumulated reports have indicated that circadian rhythm is closely related to the pathogenesis of major depressive disorder (MDD). Recently, adenosine has been identified to modulate circadian clock via adenosine A1 and A2A receptor signaling pathways. Cyclic AMP-response element binding protein (CREB) is a convergent point that plays a critical role in the pathogenesis of depression and is a downstream molecule of adenosine A1 receptor signaling pathway as an endpoint that can regulate the expression of circadian genes Period1 (Per1) and Period2 (Per2). However, whether Per mediates the development of MDD via CREB has not been elucidated. We used chronic unpredictable stress (CUS) to induce depression-like behaviors and found that it could induce decrease in p-CREB and PER1 levels in the hippocampal CA1 region in rats. Both depression-like behaviors and the decreased protein levels could be rapidly rescued by the administration of adenosine A1 receptor agonist 2-Choro-N6-cyclopentyladenosine (CCPA). Furthermore, knockdown of Per1 in hippocampal CA1 region could also induce depression-like behaviors, which could also be rescued by CCPA. Interestingly, Per2 knockdown in hippocampal CA1 region resulted in potential antidepressant-like effect. In addition, knockout of CRE sequence in the promoter regions of either Per1 or Per2 led to depression-like behaviors, which could not be rescued by CCPA. These results indicated that clock genes Per1 and Per2 play critical roles in the pathophysiology of depression and CRE sequences in the promoter regions of Per1 and Per2 may be a critical antidepressant target.