ULTRASTRUCTURE OF MOUSE VALLATE TASTE-BUDS .3. PATTERNS OF SYNAPTIC CONNECTIVITY
ULTRASTRUCTURE OF MOUSE VALLATE TASTE-BUDS .3. PATTERNS OF SYNAPTIC CONNECTIVITY
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DOI：
10.1002/cne.902700102
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发表时间：
1988-04-01
影响因子：
2.5
通讯作者：
ROPER, SD
中科院分区：
文献类型：
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作者：
KINNAMON, JC;SHERMAN, TA;ROPER, SD
我们已经使用了一系列的高压电子显微照片和计算机生成的三维重建研究的形态关系和模式的突触连接在味蕾的轮廓乳头的小鼠。对7个味蕾的40根感觉神经纤维的芽内分支进行了观察。我们确定了从味觉细胞到重建的神经纤维的突触连接，并根据先前建立的超微结构标准对突触前味觉细胞进行了分类。从这些数据中，我们能够提取重建的神经纤维的以下信息：（1）味蕾内的芽内神经纤维及其分支的形态，（2）从味蕾细胞到神经纤维的突触连接的总数，以及（3）与每个突触相关的味觉细胞类型。研究了五十六个突触。突触通常位于神经纤维突起的分支点或末端。观察到突触到单个神经纤维上的味细胞的最大数量为5。一些神经纤维没有明显的突触。暗细胞（I型）、中间细胞和亮细胞（II型）都与感觉神经纤维形成突触连接。在任何情况下，暗细胞和亮细胞都不会突触在同一个感觉神经纤维上。我们观察到，任何给定的神经纤维接受其突触输入从形态相似的味觉细胞提供的证据，在味蕾突触连接的特异性。我们推测所观察到的突触连接模式与味蕾功能有关。由于给定神经纤维上的所有突触都来自形态相似的味觉细胞，我们假设味觉细胞形态和感觉反应之间存在相关性。对味觉细胞的细胞内电生理研究将证明或反驳这一假设，其中对局部施加的化学刺激的反应随后是对相同味觉细胞的超微结构特征的表征。
We have used serial high voltage electron micrographs and computer-generated, three-dimensional reconstructions to study morphological relationships and patterns of synaptic connectivity in taste buds from the circumvallate papillae of the mouse. The intragemmal arborizations of 40 sensory nerve fibers were examined from 7 taste buds that were sectioned serially. We identified the synaptic connections from taste cells onto the reconstructed nerve fibers and classified the presynaptic taste cells based on previously established ultra-structural criteria. From these data we were able to extract the following information for the reconstructed nerve fibers: (1) the morphology of intragemmal nerve fibers and their arborizations within the taste bud, (2) the total number of synaptic connections from taste bud cells onto the nerve fibers, and (3) the taste cell types associated with each of the synapses. Fifty-six synapses were studied. Synapses were often found to be located at either the branch points or terminations of nerve fiber processes. The maximum number of taste cells observed to synapse onto a single nerve fiber was 5. Several nerve fibers had no apparent synapses. Dark cells (type I), intermediate cells, and light cell (type II) all formed synaptic connections with sensory nerve fibers. In no cases did dark cells and light cells synapse onto the same sensory nerve fiber. Our observation that any given nerve fiber receives its synaptic input from morphologically similar taste cells provides evidence for specificity in taste bud synaptic connections. We speculate that the observed pattern of synaptic connections is related to taste bud function. Since all of the synapses onto a given nerve fiber are from morphologically similar taste cells, we postulate that there is a correlation between taste cell morphology and sensory responsiveness. Intracellular electrophysiological studies on taste cells, in which response to focally applied chemical stimuli are followed by characterization of the ultrastructural features of the same taste cells, will prove or disprove this hypothesis.