Shigemoto Masaya, Nakatsuka Hiroki, Ohtubo Yoshitaka, Natsume Kiyohisa
Department of Human Intelligence Systems, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, 2-4 Hibikino, Wakamatsu-ku, Kitakyushu, Fukuoka, 808-0196 Japan.
Cogn Neurodyn. 2022 Jun;16(3):507-518. doi: 10.1007/s11571-021-09736-4. Epub 2021 Nov 10.
Animals have a diurnal rhythm with a cycle of approximately 1 day modulated by light information. This rhythm modulates memory performance. Relatedly, the hippocampal neural circuit has a dynamic property that can induce theta, beta, and gamma brain waves. However, the associated between the diurnal rhythm and these waves has not yet been elucidated. Carbachol, a cholinergic agent, can induce oscillations (e.g., beta waves) in rat hippocampal slices. In this study, we investigate the diurnal changes in the dynamic properties of hippocampal neuronal circuits using carbachol-induced beta oscillations (CIBOs). The hippocampal slices were made from rats adapted to 12-h-each light and dark conditions. The frequency of CIBO was significantly decreased more at midnight than at midday. There was no significant difference both under 12-h-each dark/dark condition and in the shuffled data of diurnal condition. The frequency at midday was significantly decreased by the application of SR95531 (gabazine) and bicuculline gamma-aminobutyric acid (GABA)-A receptor antagonists. In paired-pulse inhibition (PPI) experiments, the PPI ratio at midnight was larger than that at midday. The PPI ratio reflects the degree of recurrent inhibition. The expression level of Glutamate decarboxylase 65, an enzyme that synthetizes GABA, was significantly higher at midnight than at midday. These results suggest that the CIBO frequency can be modulated by diurnal changes of hippocampal inhibitory neurons, and the modulation may lead to a diurnal change in memory performance.
The online version contains supplementary material available at 10.1007/s11571-021-09736-4.
动物具有昼夜节律，其周期约为1天，受光信息调节。这种节律调节记忆表现。相关地，海马神经回路具有可诱发θ波、β波和γ脑电波的动态特性。然而，昼夜节律与这些脑电波之间的关联尚未阐明。卡巴胆碱是一种胆碱能药物，可在大鼠海马切片中诱发振荡（如β波）。在本研究中，我们使用卡巴胆碱诱发的β振荡（CIBOs）来研究海马神经元回路动态特性的昼夜变化。海马切片取自适应12小时光照和12小时黑暗条件的大鼠。午夜时CIBO的频率比中午时显著降低更多。在12小时全暗条件下以及昼夜条件的随机数据中均无显著差异。应用SR95531（加巴喷丁）和荷包牡丹碱γ-氨基丁酸（GABA）-A受体拮抗剂后，中午时的频率显著降低。在配对脉冲抑制（PPI）实验中，午夜时的PPI比率大于中午时的。PPI比率反映了反复抑制的程度。合成GABA的酶谷氨酸脱羧酶65的表达水平在午夜时显著高于中午时。这些结果表明，CIBO频率可受海马抑制性神经元的昼夜变化调节，且这种调节可能导致记忆表现的昼夜变化。
在线版本包含可在10.1007/s11571-021-09736-4获取的补充材料。
