Caffeine reverses sleep deprivation-induced synaptic and social memory deficits via adenosine receptor modulation in the male mouse hippocampal CA2 region.

Sleep deprivation (SD) is a critical risk factor for cognitive decline and is closely linked to psychiatric disorders. The hippocampal CA2 region is critically involved in encoding social memory and regulating emotional behavior, and it has been implicated in various neuropsychiatric conditions. However, how SD affects CA2-dependent synaptic plasticity and related behaviors remains poorly understood. Here, we subjected mice to 5 h of SD via gentle handling and examined synaptic plasticity, molecular signaling, and social recognition memory. Electrophysiological recordings revealed that SD markedly impaired long-term potentiation (LTP) in CA2 and disrupted social recognition memory, as evidenced by failure to distinguish novel from familiar conspecifics. These deficits were accompanied by upregulation of adenosine A1 receptors and PDE4A5, along with reduced expression of plasticity-related proteins including PKMζ, ERK, and BDNF. Moreover, caffeine-induced synaptic potentiation was diminished in SD mice, whereas caffeine supplementation reversed both synaptic and behavioral impairments. Together, these findings demonstrate that SD compromises CA2-dependent plasticity and social cognition through adenosine receptor signaling and identify CA2 as a vulnerable, therapeutically relevant region. Targeting adenosine pathways may represent a novel strategy to mitigate sleep loss-related cognitive dysfunction in neuropsychiatric disorders.