Jacquin M F, Stennett R A, Renehan W E, Rhoades R W
Department of Neuroscience, New York College of Osteopathic Medicine, Old Westbury 11568.
J Comp Neurol. 1988 Jan 1;267(1):107-30. doi: 10.1002/cne.902670108.
Prior studies indicate that vibrissa, guard hair, hairy skin, mucosa, and nociceptive trigeminal primary afferents give rise to morphologically distinct terminal arbors in the medullary dorsal horn. The present study describes the extent to which similar structure-function relationships exist in the rostrally adjacent subnucleus interpolaris (SpVi). Seventy-three axons were physiologically characterized and visualized by standard intra-axonal HRP labeling techniques. They responded to guard hair (GH) or vibrissa (VIB) deflection; gentle pressure applied to hairy skin (HS), glabrous skin (GS), lingual mucosa (LM), or an incisor (PER); or a noxious pinch of the face (NOX). Response latencies to trigeminal ganglion shocks were equivalent for all categories with low threshold receptive fields (mean = 0.44 ms), and these were significantly shorter than those of fibers with high threshold NOX receptive fields (mean = 0.88 ms). All axons gave off transversely oriented collaterals into SpVi with rostrocaudal discontinuities in their arbors. Collaterals were topographically organized. Axons innervating the rostral mouth and face terminated medially, and those that supplied the caudal face innervated successively more lateral SpVi. The dorsal face was represented in the ventral SpVi, whereas the ventral face and mouth were represented more dorsally. This transverse topography extended largely throughout the rostrocaudal extent of SpVi. VIB, GH, GS, and LM collaterals had similar configurations with circumscribed arbors. HS, PER, and NOX arbors had a "stringy" shape without a clear terminal focus, save for the fact that PER and NOX collaterals often terminated in rostrally displaced substantia gelatinosa at the level of the caudal SpVi. Analysis of variance, considering only those data from mystacial VIB, GH, and HS fibers, indicated significant differences for all of the following measures: number of collaterals, number of boutons per collateral, arbor area, arbor circumference, and arbor circularity (form factor). A similar analysis, considering all fiber types, indicated significant differences for only the following measures: number of collaterals, arbor area, and arbor circumference. Individual group comparisons between the more heavily sampled functional categories indicated that GH afferents had significantly fewer collaterals, fewer boutons per collateral, smaller arbor area, shorter arbor circumference, and more circular arbors than those of HS axons. VIB fibers tended to fall between GH and HS afferents with respect to number of collaterals, arbor area, circumference, and circularity. The remaining functional groups were not as orderly.(ABSTRACT TRUNCATED AT 400 WORDS)
先前的研究表明，触须、保护毛、多毛皮肤、黏膜以及伤害性三叉神经初级传入纤维在延髓背角形成形态上截然不同的终末分支。本研究描述了在紧邻头端的极间亚核（SpVi）中，类似的结构 - 功能关系存在的程度。通过标准的轴内辣根过氧化物酶（HRP）标记技术，对73条轴突进行了生理学特征鉴定和可视化。它们对保护毛（GH）或触须（VIB）的偏转、施加于多毛皮肤（HS）、无毛皮肤（GS）、舌黏膜（LM）或门齿（PER）的轻柔压力，或面部的伤害性捏压（NOX）产生反应。对于所有具有低阈值感受野的类别，对三叉神经节电击的反应潜伏期相同（平均 = 0.44毫秒），且这些潜伏期显著短于具有高阈值NOX感受野的纤维的潜伏期（平均 = 0.88毫秒）。所有轴突都发出横向的侧支进入SpVi，其分支在头尾方向上有间断。侧支按拓扑结构排列。支配头端口腔和面部的轴突在内侧终止，而供应尾端面部的轴突依次支配更外侧的SpVi。背侧面部在腹侧SpVi中代表，而腹侧面部和口腔在更背侧代表。这种横向拓扑结构在很大程度上贯穿SpVi的头尾范围。VIB、GH、GS和LM侧支具有相似的构型，有界限分明的分支。HS、PER和NOX分支呈“丝状”，没有明确的终末焦点，只是PER和NOX侧支通常在尾端SpVi水平的头端移位的胶状质中终止。仅考虑来自面部触须VIB纤维、GH纤维和HS纤维的数据进行方差分析，结果显示在以下所有测量指标上存在显著差异：侧支数量、每个侧支的终扣数量、分支面积、分支周长和分支圆度（形态因子）。考虑所有纤维类型的类似分析表明，仅在以下测量指标上存在显著差异：侧支数量、分支面积和分支周长。在抽样较多的功能类别之间进行的个体组比较表明，与HS轴突相比，GH传入纤维的侧支显著更少、每个侧支的终扣更少、分支面积更小周长更短且分支更圆。就侧支数量分支面积、周长和圆度而言，VIB纤维往往介于GH纤维和HS传入纤维之间。其余功能组则不那么有规律。（摘要截断于400字）
