REGIONALLY SELECTIVE ELIMINATION OF CUTANEOUS THERMAL NOCICEPTION IN RATS BY NEONATAL CAPSAICIN
REGIONALLY SELECTIVE ELIMINATION OF CUTANEOUS THERMAL NOCICEPTION IN RATS BY NEONATAL CAPSAICIN
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DOI：
10.1002/cne.902610409
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发表时间：
1987-07-22
影响因子：
2.5
通讯作者：
DIAMOND, J
中科院分区：
文献类型：
--
作者：
DOUCETTE, R;THERIAULT, E;DIAMOND, J
我们研究了热和机械伤害性感受麻醉的成年大鼠已接受皮下注射辣椒素作为新生儿。该处理似乎在检查的任何身体区域中均未损害机械伤害感受。与此相反，热伤害性感受存在于某些位置，而在其他位置则不存在。其从背部皮肤的完全消失与背侧皮神经（DCN）中C纤维反应性的丧失相关;这些神经的电激发现在不能引起皮肤干肌反射的延迟分量，尽管早期反射反应由机械敏感性A δ的激发引起。轴突，不受影响。热伤害性感受同样从爪的无垫无毛皮肤中消除。然而，当刺激被选择性地施加到垫上时，诱发了正常的缩足反应。通过在未处理动物中使用伊文思蓝技术揭示了爪中这种差异性热反应的可能基础;爪神经的逆向激活以激发其C纤维群导致垫周围无毛皮肤中的染料外渗，但垫本身几乎没有染料外渗，表明垫中相对缺乏伤害性C纤维神经支配。在辣椒素处理的动物中，甩尾试验显示尾部对有害热的反应显著降低。这些结果可以解释新生儿辣椒素的影响的报告中的一些异常。似乎在以爪垫和尾部为例的策略性暴露位置，辣椒素抗性轴突可能是相对快速传导的A δ。其中一种与发出有害热量的信号有关。热伤害性C纤维，似乎是唯一负责这种信号从背部皮肤和nonpad无毛皮肤的爪子可能有助于热伤害性的尾巴，但不是在爪垫。
We have studied thermal and mechanical nociception in anesthetized adult rats that had received subcutaneous injections of capsaicin as neonates. This treatment appeared not to have impaired mechanonociception in any of the body regions that were examined. In contrast, thermal nociception was present in some locations and absent in others. Its total disappearance from back skin correlated with the loss of C fiber responsiveness in the dorsal cutaneous nerves (DCNs); electrical excitation of these nerves now failed to evoke the delayed component of the cutaneous trunci muscle reflex, although the early reflex response, elicited by excitation of the mechanosensitive A.delta. axons, was unaffected. Heat nociception was similarly eliminated from the nonpad glabrous skin of the paws. When the stimulus was applied selectively to the pads, however, a normal foot-withdrawal response was evoked. The probable basis of this differential heat responsiveness in the paws was revealed by the use of the Evans Blue technique in untreated animals; antidromic activation of the paw nerves to excite their C fiber population led to dye extravasation in the glabrous skin around the pads but to almost none in the pads themselves, indicating a relative absence in the pads of a nociceptive C fiber innervation. In capsaicin-treated animals, the tail-flick test revealed a significantly reduced responsiveness to noxious heat in the tail. These results may explain some of the anomalies among the reports of the effects of neonatal capsaicin. It appears that in strategically exposed locations exemplified by the paw pads and tail, capsaicin-resistant axons that could be the relatively fast-conducting A.delta. ones are involved in the signalling of noxious heat. The heat-nociceptive C fibers that seem to be solely responsible for such signalling from back skin and nonpad glabrous skin of the paws probably contribute to heat nociception in the tail but not to that in the paw pads.