γ-frequency excitatory input to granule cells facilitates dendrodendritic inhibition in the rat olfactory bulb
γ-frequency excitatory input to granule cells facilitates dendrodendritic inhibition in the rat olfactory bulb
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DOI：
10.1152/jn.00212.2003
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发表时间：
2003-08-01
影响因子：
2.5
通讯作者：
Strowbridge, BW
中科院分区：
文献类型：
--
作者：
Halabisky, B;Strowbridge, BW
反复和侧向抑制在嗅球输出神经元--二尖瓣细胞的气味诱发放电模式中起着显著的作用。这一脑区的抑制反应是通过二尖瓣细胞树突和GABA能中间神经元之间的相互突触联系来调节的。以往的研究表明，中间神经元上的N-甲基-D-天冬氨酸(NMDA)受体在诱导树-树突触的GABA释放中起着关键作用。在急性嗅球切片中，这些受体被细胞外镁离子强直地阻断，反复抑制被禁用。在目前的研究中，我们研究了这种紧张性阻断可以被逆转的机制。我们证明，GABA能中间神经元近端树突的兴奋通路的近乎一致的激活解除了树-树突触上NMDA受体的镁离子阻断，并极大地促进了对二尖瓣细胞的反复抑制。在细胞外镁离子存在的情况下，反复和侧向抑制的门控需要伽马频率刺激颗粒细胞层中的谷氨酸能轴突。来自不同嗅觉感受器神经元亚群支配的二尖瓣细胞的长距离兴奋性轴突联系可能为颗粒细胞提供门控输入，从而促进二尖瓣细胞的侧向抑制，从而有助于气味编码。
Recurrent and lateral inhibition play a prominent role in patterning the odor-evoked discharges in mitral cells, the output neurons of the olfactory bulb. Inhibitory responses in this brain region are mediated through reciprocal synaptic connections made between the dendrites of mitral cells and GABAergic interneurons. Previous studies have demonstrated that N-methyl-D-aspartate ( NMDA) receptors on interneurons play a critical role in eliciting GABA release at reciprocal dendrodendritic synapses. In acute olfactory bulb slices, these receptors are tonically blocked by extracellular Mg2+, and recurrent inhibition is disabled. In the present study, we examined the mechanisms by which this tonic blockade could be reversed. We demonstrate that near-coincident activation of an excitatory pathway to the proximal dendrites of GABAergic interneurons relieves the Mg2+ blockade of NMDA receptors at reciprocal dendrodendritic synapses and greatly facilitates recurrent inhibition onto mitral cells. Gating of recurrent and lateral inhibition in the presence of extracellular Mg2+ requires gamma-frequency stimulation of glutamatergic axons in the granule cell layer. Long-range excitatory axon connections from mitral cells innervated by different subpopulations of olfactory receptor neurons may provide a gating input to granule cells, thereby facilitating the mitral cell lateral inhibition that contributes to odorant encoding.