Analysis of gamma rhythms in the rat hippocampus in vitro and in vivo
Analysis of gamma rhythms in the rat hippocampus in vitro and in vivo
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DOI：
10.1113/jphysiol.1996.sp021397
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发表时间：
1996-06-01
影响因子：
5.5
通讯作者：
Jefferys, JGR
中科院分区：
文献类型：
--
作者：
Traub, RD;Whittington, MA;Jefferys, JGR
1.我们以前已经用实验和计算机模型展示了如何在海马神经元网络中产生40赫兹(伽马)振荡，涉及相互的GABA(A)介导的突触抑制和紧张性兴奋性输入的来源。在这里，我们探索这个模型对大鼠在体外和活体中的一些海马网现象的影响。构建了由1024个CA3锥体细胞和256个神经元组成的模型网络。在锥体细胞和神经元间模拟AMPA(α-氨基-3-羟基-5-甲基-4-异恶唑丙酸)、NMDA(N-甲基-D-天冬氨酸)、GABA(A)和GABA(B)受体。在模型和实验中，在伽马范围内，网络振荡的频率取决于三个参数：神经元间连接的GABA(A)电导和衰减时间常数，以及神经元间的驱动电流。伽马节律模型预测锥体细胞和神经元间放电之间的平均零时滞，就像在活体大鼠的海马体中观察到的那样。该模型还复制了伽马节律，其频率随时间变化，频率为θ频率(约5赫兹)。当对枝形吊灯和篮子单元的主音信号进行5赫兹调制时，就会发生这种情况。在模型中，可以通过几种方法产生同步爆发，包括部分阻断神经元上的GABA(A)受体或AMPA受体，或通过增强AMPA介导的EPSCs。在所有这些情况下，爆发之后都会出现一条瞬间出现的伽马波的“尾巴”，这是在体内海马体中观察到的一种跟随尖锐波的现象。这条尾巴在模型中出现，是因为同步爆发延迟了神经元间的兴奋。在海马片(CA3区)和活体中，同步的癫痫样爆发后都发现了伽马活动的尾部。我们的数据表明，当神经元间池受到强直或缓慢变化的兴奋时，海马体中就会出现伽马频率的脑电活动。振荡的频率取决于这种兴奋的强度和调节神经元间抑制耦合的参数。然后，神经元间网络输出以节奏同步的IPSP的形式施加到锥体神经元上。
1. We have shown previously, with experimental and computer models, how a '40 Hz' (gamma) oscillation can arise in networks of hippocampal interneurones, involving mutual GABA(A)-mediated synaptic inhibition and a source of tonic excitatory input. Here, we explore implications of this model for some hippocampal network phenomena in the rat in, vitro and in vivo.2. A model network was constructed of 1024 CA3 pyramidal cells and 256 interneurones. AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid), NMDA (N-methyl-D-aspartate), GABA(A) and GABA(B) receptors were simulated on pyramidal cells and on interneurones.3. In both model and experiment, the frequency of network oscillations, in the gamma range, depended upon three parameters: GABA(A) conductance and decay time constant in interneurone-->interneurone connections, and the driving current to the interneurones.4. The model of gamma rhythm predicts an average zero phase lag between firing of pyramidal cells and interneurones, as observed in the rat hippocampus in vivo. The model also reproduces a gamma rhythm whose frequency changes with time, at theta frequency (about 5 Hz). This occurs when there is 5 Hz modulation of a tonic signal to chandelier and basket cells.5. Synchronized bursts can be produced in the model by several means, including partial blockade of GABA(A) receptors or of AMPA receptors on interneurones, or by augmenting AMPA-mediated EPSCs. In all of these cases, the burst can be followed by a 'tail' of transiently occurring gamma waves, a phenomenon observed in the hippocampus in vivo following sharp waves. This tail occurs in the model because of delayed excitation of the interneurones by the synchronized burst. A tail of gamma activity was found after synchronized epileptiform bursts both in the hippocampal slice (CA3 region) and in vivo.6. Our data suggest that gamma-frequency EEG activity arises in the hippocampus when pools of interneurones receive a tonic or slowly varying excitation. The frequency of the oscillation depends upon the strength of this excitation and on the parameters regulating the inhibitory coupling between the interneurones. The interneurone network output is then imposed upon pyramidal neurones in the form of rhythmic synchronized IPSPs.