Control of on/off glomerular signaling by a local GABAergic microcircuit in the olfactory bulb.
Control of on/off glomerular signaling by a local GABAergic microcircuit in the olfactory bulb.
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DOI：
10.1523/jneurosci.2368-09.2009
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发表时间：
2009-10-28
期刊：
影响因子：
--
通讯作者：
Schoppa NE
中科院分区：
文献类型：
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作者：
Gire DH;Schoppa NE
气味在嗅球的输入层面由激活的肾小球的空间图谱编码，反映了鼻子中受刺激的不同气味受体（ORs）。在此，我们利用大鼠嗅球切片的膜片钳记录和钙成像技术，研究了肾小球内局部突触处理在将这些输入模式转化为嗅球输出过程中的作用。在肾小球中观察到两种类型的转化，其中第一种产生了一种双峰的“开/关”肾小球信号，该信号根据ORN输入水平呈概率性变化。这种双峰反应行为在肾小球突触反应以及动作电位（“峰电位”）发放中均可见，其中与一个肾小球相关联的所有 mitral细胞要么长时间发放峰电位簇，要么完全不发放。此外，有证据表明，围绕一个肾小球的γ - 氨基丁酸能（GABAergic）球旁（PG）细胞可通过靶向兴奋性外丛状细胞的抑制性输入来阻止该肾小球的激活。PG细胞的激活路径似乎局限于一个肾小球，即一个肾小球的ORN引发对同一肾小球的抑制。所观察到的肾小球“自抑制”提供了一种过滤气味信号的机制，它是对通常所提出的特定OR肾小球之间侧向抑制机制的一种替代。在这种情况下，基于肾小球处PG细胞与兴奋性神经元输入电阻的差异，可以实现对微弱气味信号的选择性抑制。
Odors are coded at the input-level of the olfactory bulb by a spatial map of activated glomeruli, reflecting different odorant receptors (ORs) stimulated in the nose. Here we examined the function of local synaptic processing within glomeruli in transforming these input patterns into an output for the bulb, using patch-clamp recordings and calcium imaging in rat bulb slices. Two types of transformations were observed at glomeruli, the first of which produced a bimodal, “on/off” glomerular signal that varied probabilistically depending on ORN input levels. The bimodal response-behavior was seen in glomerular synaptic responses, as well as in action potential (“spike”)-firing, wherein all mitral cells affiliated with a glomerulus either engaged in prolonged spike bursts or did not spike at all. In addition, evidence was obtained that GABAergic periglomerular (PG) cells that surround a glomerulus can prevent activation of a glomerulus through inhibitory inputs targeted onto excitatory external tufted cells. The path of PG cell activation appeared to be confined to one glomerulus, such that ORNs at one glomerulus initiated inhibition of the same glomerulus. The observed glomerular “self-inhibition” provides a mechanism of filtering odor signals that would be an alternative to commonly-proposed mechanisms of lateral inhibition between OR-specific glomeruli. In this case, selective suppression of weak odor signals could be achieved based on the difference in the input resistance of PG cells versus excitatory neurons at a glomerulus.