Gamma-aminobutyric acid type B receptor-dependent burst-firing in thalamic neurons: a dynamic clamp study.
Gamma-aminobutyric acid type B receptor-dependent burst-firing in thalamic neurons: a dynamic clamp study.
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DOI：
10.1073/pnas.93.23.13245
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发表时间：
1996-11
影响因子：
11.1
通讯作者：
Daniel Ulrich;J. Huguenard
中科院分区：
文献类型：
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作者：
Daniel Ulrich;J. Huguenard
丘脑中的同步网络反应依赖于起源于丘脑网状核（nRt）的阶段性抑制，并由神经递质γ-氨基丁酸（GABA）介导。nRT内连接在抑制性定相中的作用仍然存在争议。最近，功能性GABA B型（GABAB）受体被证明对nRt细胞，和缓慢的时间过程中的GABAB突触反应似乎非常适合于去极化低阈值钙通道。这促进了突发放电，这是同步反应的特征。在这里，我们调查GABAB介导的反弹爆发放电在丘脑细胞。全细胞电流钳记录从nRt细胞和体感丘脑皮层中继细胞在大鼠脑片。当峰值抑制性突触后电位超极化大于-92 mV时，由混合计算机神经元突触（动态钳）产生的合成GABAB抑制性突触后电位在两种细胞类型中触发反弹低阈值钙峰。在nRt（7 nS）和丘脑皮质（5 nS）细胞中，产生反弹爆发的阈值抑制性突触后电位电导是相当的。然而，爆发开始在nRt（1秒）是相当延迟相比，丘脑皮质（0.6秒）细胞。因此，GABAB抑制性突触后电位可以在中继神经元和nRt神经元中引起低阈值钙尖峰，但是所产生的振荡频率对于丘脑皮质-nRt网络（3 Hz）比对于nRt-nRt网络（1-2 Hz）更快。因此，我们得出结论，快速（> 2 Hz）GABAB依赖性丘脑振荡主要是通过兴奋性和抑制性细胞之间的相互连接来维持的。这些发现进一步表明，当振荡神经网络包含复发和相互抑制，那么不同的人口频率可能会导致当一种或另一种类型的抑制是有利的。
Synchronized network responses in thalamus depend on phasic inhibition originating in the thalamic reticular nucleus (nRt) and are mediated by the neurotransmitter gamma-aminobutyric acid (GABA). A suggested role for intra-nRt connectivity in inhibitory phasing remains controversial. Recently, functional GABA type B (GABAB) receptors were demonstrated on nRt cells, and the slow time course of the GABAB synaptic response seems ideally suited to deinactivate low-threshold calcium channels. This promotes burst firing, a characteristic feature of synchronized responses. Here we investigate GABAB-mediated rebound burst firing in thalamic cells. Whole-cell current-clamp recordings were obtained from nRt cells and somatosensory thalamocortical relay cells in rat brain slices. Synthetic GABAB inhibitory postsynaptic potentials, generated by a hybrid computerneuron synapse (dynamic clamp), triggered rebound low-threshold calcium spikes in both cell types when peak inhibitory postsynaptic potential hyperpolarization was greater than -92 mV. The threshold inhibitory postsynaptic potential conductance for rebound burst generation was comparable in nRt (7 nS) and thalamocortical (5 nS) cells. However, burst onset in nRt (1 s) was considerably delayed compared with thalamocortical (0.6 s) cells. Thus, GABAB inhibitory postsynaptic potentials can elicit low-threshold calcium spikes in both relay and nRt neurons, but the resultant oscillation frequency would be faster for thalamocortical-nRt networks (3 Hz) than for nRt-nRt networks (1-2 Hz). We conclude, therefore, that fast (> 2 Hz) GABAB-dependent thalamic oscillations are maintained primarily by reciprocal connections between excitatory and inhibitory cells. These findings further indicate that when oscillatory neural networks contain both recurrent and reciprocal inhibition, then distinct population frequencies may result when one or the other type of inhibition is favored.