Table_1_Chronic caffeine consumption curbs rTMS-induced plasticity.pdf

BackgroundCaffeine is a widely used psychostimulant. In the brain, caffeine acts as a competitive, non-selective adenosine receptor antagonist of A1 and A2A, both known to modulate long-term potentiation (LTP), the cellular basis of learning and memory. Repetitive transcranial magnetic stimulation (rTMS) is theorized to work through LTP induction and can modulate cortical excitability as measured by motor evoked potentials (MEPs). The acute effects of single caffeine doses diminish rTMS-induced corticomotor plasticity. However, plasticity in chronic daily caffeine users has not been examined.
MethodWe conducted a post hoc secondary covariate analysis from two previously published plasticity-inducing pharmaco-rTMS studies combining 10 Hz rTMS and D-cycloserine (DCS) in twenty healthy subjects.
ResultsIn this hypothesis-generating pilot study, we observed enhanced MEP facilitation in non-caffeine users compared to caffeine users and placebo.
ConclusionThese preliminary data highlight a need to directly test the effects of caffeine in prospective well-powered studies, because in theory, they suggest that chronic caffeine use could limit learning or plasticity, including rTMS effectiveness.

研究背景：咖啡因是一种广泛使用的精神兴奋剂。在大脑中，咖啡因可作为A1与A2A型腺苷受体的竞争性非选择性拮抗剂，而这两种受体均已知可调控长时程增强（long-term potentiation, LTP）——这是学习与记忆的细胞基础。重复经颅磁刺激（repetitive transcranial magnetic stimulation, rTMS）的作用机制被认为是通过诱导长时程增强，并可通过运动诱发电位（motor evoked potentials, MEPs）检测的方式调节皮层兴奋性。单次咖啡因剂量的急性效应会削弱重复经颅磁刺激诱导的皮质运动可塑性，但目前尚未针对每日长期饮用咖啡因的人群的可塑性变化开展研究。
研究方法：本研究对两项已发表的诱导可塑性的药物-重复经颅磁刺激联合研究进行事后二次协变量分析，两项研究均将10Hz重复经颅磁刺激与D-环丝氨酸（D-cycloserine, DCS）联合应用，共纳入20名健康受试者。
研究结果：在这项假说生成性预试验中，我们观察到，与咖啡因摄入人群及安慰剂组相比，无咖啡因摄入人群的运动诱发电位易化作用显著增强。
研究结论：这些初步数据凸显了开展前瞻性效力充足的研究以直接验证咖啡因效应的必要性，因为本研究理论上提示长期咖啡因摄入可能会损害学习或可塑性，包括重复经颅磁刺激的应用效果。