Waite P M, de Permentier P J
School of Anatomy, University of New South Wales, Sydney, Australia.
J Comp Neurol. 1997 Sep 8;385(4):599-615. doi: 10.1002/(sici)1096-9861(19970908)385:4<599::aid-cne6>3.0.co;2-z.
In the present study, we investigated the effect of neonatally administered capsaicin on whisker-related pattern formation in the rat trigeminal complex. Both normal whisker-related patterns of barrelettes and the modified patterns seen after neonatal section of the infraorbital nerve were assessed. Capsaicin caused no change in the pattern or size of cytochrome oxidase (CO) barrelettes in the principal trigeminal nucleus (Vp) or trigeminal nucleus interpolaris (Vi) or caudalis (Vc). Injections of horseradish peroxidase (HRP) or wheatgerm agglutinin conjugated to HRP (WGA-HRP) into the posteroorbital (PO) whisker follicle in vehicle-treated animals showed that WGA labelled a larger number of trigeminal ganglion cells than HRP (203 +/- 23; cf. 158 +/- 19), with an increased labelling of small-diameter neurons (HRP: 25.9 +/- 7.7 microm; WGA: 23.2 +/- 7.2 pm). Capsaicin caused a loss of smaller diameter cells but had no effect on the location, cross-sectional area, or rostrocaudal extent of the transganglionically labelled HRP terminations in Vp, Vi, Vc, and cervical dorsal horn. WGA-HRP labelling revealed similar, but less dense, central terminal areas as HRP and an additional area of superficial terminals in the caudal medulla; these were also unaffected by capsaicin treatment. After infraorbital nerve section, CO patches and transganglionically labelled afferent terminations, corresponding to innervated nonmystacial whiskers, were approximately doubled in size. Capsaicin had no effect on the increased size of these spared whisker patches or their afferent terminal areas. These results suggest that barrelette formation is not dependent on unmyelinated afferents and that the changes in response properties seen after capsaicin, such as increased receptive fields, reflect functional changes rather than anatomical expansion of afferent terminal areas.
在本研究中，我们调查了新生期给予辣椒素对大鼠三叉神经复合体中与触须相关的模式形成的影响。评估了正常的小桶状结构相关触须模式以及眶下神经新生期切断后出现的改变模式。辣椒素对三叉神经主核（Vp）、三叉神经极间核（Vi）或尾侧核（Vc）中细胞色素氧化酶（CO）小桶状结构的模式或大小没有影响。在给予溶剂处理的动物的眶后（PO）触须毛囊中注射辣根过氧化物酶（HRP）或与HRP偶联的麦胚凝集素（WGA-HRP），结果显示WGA标记的三叉神经节细胞数量比HRP多（203±23；相比之下，HRP为158±19），并且小直径神经元的标记增加（HRP：25.9±7.7微米；WGA：23.2±7.2皮米）。辣椒素导致较小直径细胞减少，但对Vp、Vi、Vc和颈背角中经神经节标记的HRP终末的位置、横截面积或 rostrocaudal范围没有影响。WGA-HRP标记显示与HRP相似但密度较低的中央终末区域以及延髓尾部的一个额外的浅表终末区域；这些也不受辣椒素处理的影响。眶下神经切断后，对应于受支配的非触须触须的CO斑块和经神经节标记的传入终末大小大约增加了一倍。辣椒素对这些保留的触须斑块及其传入终末区域的增大没有影响。这些结果表明小桶状结构的形成不依赖于无髓传入纤维，并且辣椒素处理后观察到的反应特性变化，如感受野增加，反映的是功能变化而非传入终末区域的解剖学扩张。
