Department of Movement Sciences, Movement Control & Neuroplasticity Research Group, Group Biomedical Sciences, KU Leuven, Heverlee, Belgium; REVAL Research Institute, Faculty of Rehabilitation Sciences, Hasselt University, Agoralaan Building A, 3590 Diepenbeek, Belgium.
Department of Movement Sciences, Movement Control & Neuroplasticity Research Group, Group Biomedical Sciences, KU Leuven, Heverlee, Belgium.
Neuroimage. 2021 Feb 1;226:117536. doi: 10.1016/j.neuroimage.2020.117536. Epub 2020 Nov 10.
Healthy aging is associated with mechanistic changes in gamma-aminobutyric acid (GABA), the most abundant inhibitory neurotransmitter in the human brain. While previous work mainly focused on magnetic resonance spectroscopy (MRS)-based GABA+ levels and transcranial magnetic stimulation (TMS)-based GABA receptor (GABAR) activity in the primary sensorimotor (SM1) cortex, the aim of the current study was to identify age-related differences in positron emission tomography (PET)-based GABAR availability and its relationship with GABA+ levels (i.e. GABA with the contribution of macromolecules) and GABAR activity. For this purpose, fifteen young (aged 20-28 years) and fifteen older (aged 65-80 years) participants were recruited. PET and MRS images were acquired using simultaneous time-of-flight PET/MR to evaluate age-related differences in GABAR availability (distribution volume ratio with pons as reference region) and GABA+ levels. TMS was applied to identify age-related differences in GABAR activity by measuring short-interval intracortical inhibition (SICI). Whereas GABAR availability was significantly higher in the SM cortex of older as compared to young adults (18.5%), there were neither age-related differences in GABA+ levels nor SICI. A correlation analysis revealed no significant associations between GABAR availability, GABAR activity and GABA+ levels. Although the exact mechanisms need to be further elucidated, it is possible that a higher GABAR availability in older adults is a compensatory mechanism to ensure optimal inhibitory functionality during the aging process.
健康老龄化与γ-氨基丁酸（GABA）的机制变化有关，GABA 是人类大脑中最丰富的抑制性神经递质。虽然之前的工作主要集中在基于磁共振波谱（MRS）的 GABA+水平和基于经颅磁刺激（TMS）的 GABA 受体（GABAR）在初级感觉运动（SM1）皮层中的活性，但当前研究的目的是确定正电子发射断层扫描（PET）-基于 GABAR 可用性及其与 GABA+水平（即 GABA 与大分子的贡献）和 GABAR 活性的关系。为此，招募了 15 名年轻（年龄 20-28 岁）和 15 名老年（年龄 65-80 岁）参与者。使用同时飞行时间 PET/MR 采集 PET 和 MRS 图像，以评估 GABAR 可用性（以桥脑为参考区域的分布容积比）和 GABA+水平的年龄相关性差异。TMS 用于通过测量短间隔皮质内抑制（SICI）来确定 GABAR 活性的年龄相关性差异。虽然老年组 SM 皮层中的 GABAR 可用性明显高于年轻组（18.5%），但 GABA+水平和 SICI 与年龄无关。相关性分析显示 GABAR 可用性、GABAR 活性与 GABA+水平之间无显著相关性。尽管确切的机制尚需进一步阐明，但老年人中较高的 GABAR 可用性可能是一种补偿机制，可确保衰老过程中抑制功能的最佳化。
