Hentschke Harald, Perkins Mark G, Pearce Robert A, Banks Matthew I
Department of Anesthesiology, University of Wisconsin, 1300 University Avenue, Madison, WI 53706, USA.
Eur J Neurosci. 2007 Sep;26(6):1642-56. doi: 10.1111/j.1460-9568.2007.05779.x.
theta (4-12 Hz) and gamma (40-90) oscillations are prominent rhythms in the mammalian brain. A striking feature of these rhythms, possibly vital to memory encoding, is their specific coordination in a manner that has been termed 'nesting', i.e. the preferred occurrence of bouts of gamma activity during specific phases of theta. Both rhythms are shaped by the neuromodulator acetylcholine, but it is unknown to what degree their coordination is influenced by cholinergic neuromodulation. Here, we investigated the effects of a blockade of muscarinic acetylcholine receptors by atropine on theta and gamma oscillations, and their interaction, in mouse hippocampus in vivo. Multi-site recordings from area CA1 of freely moving mice showed that under control conditions gamma activity was amplitude-modulated at theta frequencies. This coordination of theta and gamma oscillations, as assessed by cross-correlation of theta with the gamma envelope, was prominent in basal and apical dendritic laminae but not in intermediate laminae. It was stronger during active exploration than during awake immobility. Atropine (50 mg/kg intraperitoneal) altered several aspects of the individual and nested rhythms. It rendered theta activity irregular, decreased theta oscillation frequency and reduced gamma power. Atropine also reduced the amplitude-modulation of gamma oscillations at theta frequencies, in part by perturbing the coordination of the rhythms on a short time scale. Thus, our findings demonstrate that phase locking of the amplitude of gamma oscillations to theta in hippocampal area CA1 is partially governed by neuronal elements harbouring muscarinic receptors.
θ波（4 - 12赫兹）和γ波（40 - 90赫兹）振荡是哺乳动物大脑中的显著节律。这些节律的一个显著特征，可能对记忆编码至关重要，即它们以一种被称为“嵌套”的方式进行特定协调，也就是说，γ活动在θ波的特定阶段优先出现。这两种节律均受神经调质乙酰胆碱的影响，但它们的协调在多大程度上受胆碱能神经调节的影响尚不清楚。在此，我们研究了阿托品阻断毒蕈碱型乙酰胆碱受体对小鼠海马体内θ波和γ波振荡及其相互作用的影响。对自由活动小鼠CA1区进行多部位记录显示，在对照条件下，γ活动以θ频率进行幅度调制。通过θ波与γ波包络的互相关评估，θ波和γ波振荡的这种协调在基底和顶端树突层中很显著，但在中间层中不显著。在主动探索期间比清醒不动时更强。阿托品（腹腔注射50毫克/千克）改变了单个节律和嵌套节律的几个方面。它使θ活动变得不规则，降低了θ振荡频率并降低了γ功率。阿托品还降低了γ振荡在θ频率下的幅度调制，部分原因是在短时间尺度上干扰了节律的协调。因此，我们的研究结果表明，海马体CA1区γ振荡幅度与θ波的锁相部分受含有毒蕈碱受体的神经元成分控制。
