ORGANIZATION OF INHIBITION IN THE RAT OLFACTORY-BULB EXTERNAL PLEXIFORM LAYER
ORGANIZATION OF INHIBITION IN THE RAT OLFACTORY-BULB EXTERNAL PLEXIFORM LAYER
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DOI：
10.1152/jn.1993.70.1.263
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发表时间：
1993-07-01
影响因子：
2.5
通讯作者：
SCOTT, JW
中科院分区：
文献类型：
--
作者：
EZEH, PI;WELLIS, DP;SCOTT, JW
1.在电顺向刺激嗅神经层（ONL）和逆向刺激外侧嗅束和后梨状皮质（pPC）的过程中，对大鼠嗅球输出神经元（僧帽细胞和簇状细胞）进行细胞内记录，以测试神经元类型之间的生理差异。这些神经元中的许多是通过细胞内注射生物胞素来鉴定的，其他的是通过它们的逆向激活模式来鉴定的。标记和未标记的二尖瓣细胞表现出大的抑制性突触后电位（IPSPs）在响应于逆向刺激的PPC，而簇状细胞表现出小的IPSPs在响应于PPC刺激。然而，簇状细胞在ONL刺激下表现出较大的IPSPs。在许多情况下，这些簇状细胞对ONL刺激的反应大于二尖瓣细胞的反应。标记的表面簇状细胞，即在外丛状层（EPL）的浅表亚层中具有基底树突的细胞，对pPC刺激的反应具有最小的IPSPs。这些数据支持解剖学观察，提示二尖瓣和浅表簇状细胞负责IPSP的颗粒细胞群可能是不同的。不同类型的输出细胞对顺向刺激的反应也存在差异。I型二尖瓣细胞，其基底树突局限于深亚层的EPL，是显着不兴奋ONL刺激比II型二尖瓣细胞，其基底树突分布在中间亚层的EPL。一半的I型二尖瓣细胞不能被ONL刺激兴奋。表浅簇状细胞比II型二尖瓣细胞表现出更强的顺向兴奋性，通常对ONL刺激有两个或多个棘波反应. IPSPs在表面簇状细胞的离子基础出现类似的二尖瓣细胞所描述的。这些IPSPs可被氯离子注入逆转，并与膜电导增加有关.对于二尖瓣和簇状细胞，引起IPSP的ONL电极的数量大于引起尖峰的数量。这些数据表明，从ONL到这些细胞的输入是一种中心-环绕组织，尽管这还不意味着这些输出细胞的感觉感受野具有中心-环绕组织。总之，大鼠嗅球输出细胞的特性与其基底树突所在的EPL亚层相关。那些在浅表层中具有基底树突的细胞（浅表簇状细胞）最容易被ONL刺激激活，那些在深层中具有基底树突的细胞（I型二尖瓣细胞）最不容易被激活，而那些在中间层中具有基底树突的细胞（II型二尖瓣细胞、中间簇状细胞和内部簇状细胞）在通过该途径激活的容易性方面是中间的。基底树突在浅表亚层中的细胞从pPC的刺激中得到非常小的抑制，其通过激活更深亚层中具有棘的颗粒细胞来强烈抑制其他两个亚层的细胞。事实上，二尖瓣和表面簇状细胞产生大的氯离子依赖性IPSP响应于不同的输入表明，这里观察到的不同的电生理特性可能是由于细胞的连接性，而不是IPSP机制的任何差异。
1. Intracellular recordings were made from the output neurons (mitral and tufted cells) of the rat olfactory bulb during electrical orthodromic stimulation of the olfactory nerve layer (ONL) and antidromic stimulation of the lateral olfactory tract and posterior piriform cortex (pPC) to test for physiological differences among the neuron types. Many of these neurons were identified by intracellular injections of biocytin, and others were identified by their pattern of antidromic activation.2. Both marked and unmarked mitral cells showed large inhibitory postsynaptic potentials (IPSPs) in response to antidromic stimulation of the pPC, whereas tufted cells exhibited small IPSPs in response to pPC stimulation. Tufted cells, however, showed large IPSPs in response to ONL stimulation. In many cases, these tufted cell responses to ONL stimulation were larger than the mitral cell responses. The marked superficial tufted cells, those with basal dendrites in the superficial sublayer of the external plexiform layer (EPL), had the smallest IPSPs in response to pPC stimulation. These data support anatomic observations suggesting that the granule cell populations responsible for the IPSPs may be different for mitral and for superficial tufted cells.3. The different types of output cells also showed differences in their responses to orthodromic stimulation. Type I mitral cells, which have basal dendrites confined to the deep sublayer of the EPL, were significantly less excitable by ONL stimulation than were the type II mitral cells, which have basal dendrites distributed within the intermediate sublayer of the EPL. Half of the type I mitral cells could not be excited at all by ONL stimulation. Superficial tufted cells showed even greater orthodromic excitability than type II mitral cells, usually responding to ONL stimulation with two or more spikes.4. The ionic basis of the IPSPs in the superficial tufted cells appeared similar to those described for mitral cells. These IPSPs could be reversed by chloride injection and were associated with increased membrane conductance.5. For both mitral and tufted cells, the number of ONL electrodes evoking IPSPs was greater than the number evoking spikes. These data suggest a kind of center-surround organization of inputs to these cells from the ONL, although this does not yet imply that the sensory receptive field of these output cells has a center-surround organization.6. In conclusion, the properties of rat olfactory bulb output cells correlate with the sublayers of the EPL in which their basal dendrites lie. Those with basal dendrites in the superficial sublayer (superficial tufted cells) are most easily activated by ONL stimulation, those with basal dendrites in the deep sublayer (type I mitral cells) are least easily activated, and those with basal dendrites in the intermediate layer (type II mitral cells, intermediate tufted cells, and internal tufted cells) are intermediate in ease of activation through this route. The cells with basal dendrites in the superficial sublayer receive very little inhibition from stimulation of the pPC, which strongly inhibits cells of the other two sublayers by activating the granule cells with spines in the deeper sublayers. The fact that both mitral and superficial tufted cells produce large chloride-dependent IPSPs in response to different inputs suggests that the different electrophysiological properties observed here may be due to the connectivity of the cells rather than to any differences in the IPSP mechanisms.