GABAergic control of the ascending input from the median raphe nucleus to the limbic system.
GABAergic control of the ascending input from the median raphe nucleus to the limbic system.
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GABA能控制从中缝核到边缘系统的上行输入。
DOI：
10.1152/jn.00379.2005
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
Kocsis,Bernat
中科院分区：
文献类型：
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作者：
Li,Shaomin;Varga,Viktor;Sik,Attila;Kocsis,Bernat
中缝核（MRN）是边缘系统血清素能传入的主要来源，通常被认为可以抑制海马θ振荡。 GABA 受体在 MRN 中由血清素能和非血清素能细胞表达，包括 GABA 能和谷氨酸能神经元。本研究调查了 MRN 中 GABA 音调波动导致海马 θ 节律诱导或抑制的机制。我们发现通过反向微透析应用 GABAA 激动剂蝇蕈醇 (0.05–1.0 mM) 或 GABAA 激动剂巴氯芬 (0.2 mM) 的 MRN 具有很强的 θ 促进作用。以低浓度（0.1、0.2 mM）输注的 GABAA 拮抗剂荷包牡丹碱可消除 θ 节律。 46% 的大鼠在海马去同步化之前出现一段短时间高于正常频率的 θ 活动。较高浓度的荷包牡丹碱（0.5、1.0、2.0 mM）会导致双相反应，最初是短暂的（<10 分钟）海马去同步化，随后是稳定的 θ 节律，只要继续输注，该节律就会持续。 θ 波的频率和振幅高于对照记录，并且振荡表现出明显的间歇性特征。通过同时输注 GABABantagonist CGP35348，可完全（0.5 mM 荷包牡丹碱）或部分（1.0 mM 荷包牡丹碱）阻断由 MRN 施用荷包牡丹碱引起的海马 θ 节律。我们的研究结果表明，GABA 能网络在 MRN 中可能具有两种相反的功能：解除 θ 发生器的血清素能抑制，并通过波动的 GABA 音调调节 θ 促进电路的活性。这两种机制可能涉及不同的功能。
The median raphe nucleus (MRN) is the primary source of serotonergic afferents to the limbic system that are generally considered to suppress hippocampal theta oscillations. GABA receptors are expressed in the MRN by serotonergic and nonserotonergic cells, including GABAergic and glutamatergic neurons. This study investigated the mechanisms by which the fluctuating GABA tone in the MRN leads to induction or suppression of hippocampal theta rhythm. We found that MRN application of the GABAAagonist muscimol (0.05–1.0 mM) or GABABagonist baclofen (0.2 mM) by reverse microdialysis had strong theta promoting effects. The GABAAantagonist bicuculline infused in low concentrations (0.1, 0.2 mM) eliminated theta rhythm. A short period of theta activity of higher than normal frequency preceded hippocampal desynchronization in 46% of rats. Bicuculline in larger concentrations (0.5, 1.0, 2.0 mM) resulted in a biphasic response of an initial short (<10 min) hippocampal desynchronization followed by stable theta rhythm that lasted as long as the infusion continued. The frequency and amplitude of theta waves were higher than in control recordings and the oscillations showed a conspicuous intermittent character. Hippocampal theta rhythm elicited by MRN administration of bicuculline could be completely (0.5 mM bicuculline) or partially (1.0 mM bicuculline) blocked by simultaneous infusion of the GABABantagonist CGP35348. Our findings suggest that the GABAergic network may have two opposing functions in the MRN: relieving the theta-generators from serotonergic inhibition and regulating the activity of a theta-promoting circuitry by the fluctuating GABA tone. The two mechanisms may be involved in different functions.