Noradrenergic suppression of synaptic transmission may influence cortical signal-to-noise ratio
Noradrenergic suppression of synaptic transmission may influence cortical signal-to-noise ratio
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DOI：
10.1152/jn.1997.77.6.3326
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发表时间：
1997-06-01
影响因子：
2.5
通讯作者：
Cekic, M
中科院分区：
文献类型：
--
作者：
Hasselmo, ME;Linster, C;Cekic, M
去甲肾上腺素已被提议影响皮质结构内的信噪比，但这种影响背后的确切细胞机制尚未详细描述。在这里，我们提供了有关去甲肾上腺素细胞效应的数据，该效应可能有助于影响信噪比。在大鼠梨状（嗅觉）皮层的脑切片制备物中，去甲肾上腺素的灌注会导致皮层锥体细胞中含有突触的层（Ib 层）的兴奋性突触电位受到剂量依赖性抑制，而对传入纤维层（Ia 层）的突触电位影响较弱。去甲肾上腺素的作用在剂量反应特征和层流选择性方面与胆碱能激动剂卡巴胆碱的作用相似，并且两种激动剂的联合灌注产生与单一激动剂的等效浓度相似的作用。在梨状皮层的计算模型中，我们分析了去甲肾上腺素能抑制突触传递对信噪比的影响。相对于接收直接传入输入的神经元的活动，选择性抑制兴奋性内在连接会降低建模神经元的背景活动。这可以解释为信噪比的增加，但术语“噪声”并不能准确地表征依赖于激发的内在传播的活动，这可以更准确地描述为解释或检索。蓝斑活动介导的去甲肾上腺素水平的增加似乎增强了外部输入对皮质表征的影响，允许去甲肾上腺素脉冲在唤醒环境中介导具有环境变量强烈影响的记忆的形成。
Norepinephrine has been proposed to influence signal-to-noise ratio within cortical structures, but the exact cellular mechanisms underlying this influence have not been described in detail. Here we present data on a cellular effect of norepinephrine that could contribute to the influence on signal-to-noise ratio. In brain slice preparations of the rat piriform (olfactory) cortex, perfusion of norepinephrine causes a dose-dependent suppression of excitatory synaptic potentials in the layer containing synapses among pyramidal cells in the cortex (layer Ib), while having a weaker effect on synaptic potentials in the afferent fiber layer (layer Ia). Effects of norepinephrine were similar in dose-response characteristics and laminar selectivity to the effects of the cholinergic agonist carbachol, and combined perfusion of both agonists caused effects similar to an equivalent concentration of a single agonist. In a computational model of the piriform cortex, we have analyzed the effect of noradrenergic suppression of synaptic transmission on signal-to-noise ratio. The selective suppression of excitatory intrinsic connectivity decreases the background activity of modeled neurons relative to the activity of neurons receiving direct afferent input. This can be interpreted as an increase in signal-to-noise ratio, but the term noise does not accurately characterize activity dependent on the intrinsic spread of excitation, which would more accurately be described as interpretation or retrieval. Increases in levels of norepinephrine mediated by locus coeruleus activity appear to enhance the influence of extrinsic input on cortical representations, allowing a pulse of norepinephrine in an arousing context to mediate formation of memories with a strong influence of environmental variables.