RESPONSIVENESS AND FUNCTIONAL ATTRIBUTES OF ELECTRICALLY LOCALIZED TERMINALS OF CUTANEOUS C-FIBERS INVIVO AND INVITRO
RESPONSIVENESS AND FUNCTIONAL ATTRIBUTES OF ELECTRICALLY LOCALIZED TERMINALS OF CUTANEOUS C-FIBERS INVIVO AND INVITRO
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DOI：
10.1152/jn.1992.68.2.581
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发表时间：
1992-08-01
影响因子：
2.5
通讯作者：
HANDWERKER, HO
中科院分区：
文献类型：
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作者：
KRESS, M;KOLTZENBURG, M;HANDWERKER, HO
1. 本研究的目的是比较无髓鞘皮肤单位在体内和体外的反应性，并确定支配大鼠毛皮肤的初级传入神经对短暂的机械或热刺激没有反应的比例。在测试对适当刺激的敏感性之前，我们采用电搜索策略来定位无髓鞘纤维的末端树突。共研究了144个无髓鞘细胞，其中31个来自体内，113个来自体外。对55例慢性交感神经切除术后的神经事件进行了研究。从被切除交感神经的大鼠身上记录下来的神经单元在传导速度、电阈值或接受性方面与完整动物的神经单元并无不同。在体内和体外记录的单位性质之间只有微小的差异。这可能反映了设置的技术差异，而不是体外条件引入的生物学变化。除了体外机械冷敏感单位的患病率较高外，受体类型分布之间无显著差异。在体内记录的31个单位中有8个（26%），在体外实验中获得的113个单位中有17个（15%）对短暂的机械或热刺激没有反应。在体内，八个最初无反应的单元中的一个被反复的机械和热刺激激活。另外两个单位在局部应用芥末油后也有反应。在体外，17个无反应单位中有2个通过反复刺激被激活。其余10个无反应的单位用炎症介质联合治疗。其中4个单元被激活，3个单元发展为持续活动，2个单元也对机械和/或热刺激产生反应。第四单元对探查有反应，但没有自发活动。我们的结论是，短暂的机械或热刺激可以激发大多数无髓鞘的皮肤单位。然而，在体内和体外，部分无髓鞘单位最初甚至对有害形式的刺激也没有反应。因为在切除交感神经的准备中也会遇到那些无反应的单位，而且因为一些单位可以被反复的有害刺激或炎症剂招募，所以它们不太可能都是交感神经传出神经。引起“正常”伤害感受器致敏的相同物质能够招募最初无反应的无髓鞘传入神经。
1. The purpose of the present study was to compare the responsiveness of unmyelinated cutaneous units in vivo and in vitro and to determine the proportion of primary afferents innervating the rat hairy skin that do not respond to transient mechanical or thermal stimuli. We have adopted electrical search strategies to locate the terminal arborization of unmyelinated fibers before testing the sensitivity to adequate stimuli.2. A total of 144 unmyelinated units were studied, of which 31 were obtained from in vivo and 113 from in vitro experiments. 55 afferents were investigated after chronic surgical sympathectomy. Units recorded from sympathectomized rats did not differ in their conduction velocity, electrical thresholds, or receptive properties from units in intact animals.3. There were only minor differences between the properties of units recorded in vivo and in vitro. This probably reflects technical differences of the setups rather than biological changes introduced by the in vitro conditions. Except for a higher prevalence of mechano-cold sensitive units in vitro, there was no significant difference between the distributions of receptor types.4. Eight of 31 units (26%) recorded in vivo and 17 of 113 units (15%) obtained from in vitro experiments failed to respond to transient mechanical or thermal stimuli. In vivo, one of eight initially unresponsive units was activated by repeated mechanical and thermal stimulation. Two further units became responsive after topical application of mustard oil. In vitro, 2 of 17 unresponsive units were activated by repeated stimulation. Ten of the remaining unresponsive units were treated with a combination of inflammatory mediators. Four of these units were activated: three developed ongoing activity, and two of them also became responsive to mechanical and/or heat stimuli. The fourth unit responded to probing but was not spontaneously active.5. We conclude that transient mechanical or thermal stimuli can excite the majority of unmyelinated cutaneous units. However, in vivo and in vitro, part of unmyelinated units are initially unresponsive even to noxious forms of stimulation. Because those unresponsive units were also encountered in sympathectomized preparations, and because some units can be recruited with repeated noxious stimuli or inflammatory agents, it is unlikely that all of them are sympathetic efferents. The same substances that cause sensitization of "normal" nociceptors are capable of recruiting initially unresponsive unmyelinated afferents.