CORRELATION OF FILIFORM HAIR POSITION WITH SENSORY AFFERENT MORPHOLOGY AND SYNAPTIC CONNECTIONS IN THE 2ND INSTAR COCKROACH
CORRELATION OF FILIFORM HAIR POSITION WITH SENSORY AFFERENT MORPHOLOGY AND SYNAPTIC CONNECTIONS IN THE 2ND INSTAR COCKROACH
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DOI：
10.1002/cne.903200206
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发表时间：
1992-06-08
影响因子：
2.5
通讯作者：
BACON, JP
中科院分区：
文献类型：
--
作者：
THOMPSON, KSJ;BLAGBURN, JM;BACON, JP
本文试图将二龄美洲大蠊宫颈丝状毛的分布与其传入神经元的形态和突触连接模式联系起来。我们研究了39根常见的丝状毛发中最远端的25根。宫颈细胞体的钴填充染色丝状传入树枝。发现了3种基本乔木类型，其中2种与一龄内(M)和外侧(L)传入的乔木相似，另一种为新类型。L类型乔木可分为四个亚型。冠型最明显的相关性是宫颈毛发的周向位置。感受器在每个宫颈节段内的近远端位置也是其茎的决定因素。通过毛位和传入形态的比较，我们能够归因于二龄毛和成虫纵向毛柱成员之间的同源性。通过记录单个丝状毛发直接机械移位引起的巨型中间神经元(GIs)的突触电位，确定传入神经元与GI1、2、3、5和6之间的单突触联系模式。以从刺激开始到第一兴奋性突触后电位(EPSP)上升相的潜伏期作为单突触的判断标准。在GI输入阻力没有明显降低的情况下，L和M两个原始传入的EPSP波幅在2龄时减半。其他传入神经元可分为两类：一类是G15传入(M型)，另一类是G13、G16传入(L型)。前者与中央或中间位置相关，而后者与位于颈椎侧方的一组传入神经相关。在节段3和4，GIS1和GIS2的输入也与颈椎内侧位置相关，然而，在更近端的节段5和6，所有位置的传入都输入到这些中间神经元。相同形态和相似连接性的传入在不同节段的相同位置上的出现表明，每个感觉神经元是由其在节段内的二维位置决定的。具有相同形态的传入神经元在突触连接的近端和远端表现出差异，而其他尽管具有L型形态但具有M型连接的传入神经元的存在，意味着解剖学通常不能很好地预测突触连接。
An attempt is made to relate the distribution of filiform hairs on the cercus of the second instar cockroach, Periplaneta americana, to the morphology and patterns of synaptic connectivity of their afferents. We studied the most distal 25 of the 39 filiform hairs which are commonly present. Filiform afferent arborizations were stained by cobalt filling from the cell body in the cercus. Three fundamental arbor types were found, two similar to those of the first instar medial (M) and lateral (L) afferents, and a third, novel type. L-type arbors could be divided into four subtypes. The most obvious correlate of arbor type is the circumferential position of the hair on the cercus. The proximodistal position of the sensillum within each cercal segment is also a determinant of its arbor. By comparison of hair positions and afferent morphologies, we were able to ascribe homologies between the second instar hairs and members of adult longitudinal hair columns. The patterns of monosynaptic connections between afferents and giant interneurons (GIs) 1, 2, 3, 5, and 6 were determined by recording synaptic potentials in GIs evoked by direct mechanical displacement of individual filiform hairs. Latency from stimulus onset to the rise phase of the first excitatory postsynaptic potential (EPSP) was used as the criterion of monosynapticity. The EPSP amplitudes of the two original L and M afferents are halved in the second instar, in the absence of a significant decrease in GI input resistance. The other afferents can be divided into two basic classes: those which input to G15 (M-type), and those which input to G13 and G16 (L-type). The former is correlated with a central or medial position, while the latter is associated with a group of afferents situated laterally on the cercus. In segments 3 and 4, input to GIs 1 and 2 also correlates with a medial cercal position, however, in the more proximal segments 5 and 6, afferents at all positions input to these interneurons. The occurrence of afferents of identical morphology and similar connectivity in equivalent positions in different segments suggests that each sensory neuron is determined by its two-dimensional position within a segment. The presence of afferents with the same morphology which display proximodistal differences in synaptic connectivity, and of other afferents which have M-type connectivity despite L-type morphology, means that anatomy is generally a poor predictor of synaptic connectivity.