Simone Donald A, Zhang Xijing, Li Jun, Zhang Jun-Ming, Honda Christopher N, LaMotte Robert H, Giesler Glenn J
Department of Oral Sciences, University of Minnesota, Minneapolis, Minnesota 55455, USA.
J Neurophysiol. 2004 Jan;91(1):213-22. doi: 10.1152/jn.00527.2003.
We investigated the role of mechanosensitive spinothalamic tract (STT) neurons in mediating 1) the itch evoked by intradermal injection of histamine, 2) the enhanced sense of itch evoked by innocuous stroking (alloknesis), and 3) the enhanced pain evoked by punctate stimulation (hyperalgesia) of the skin surrounding the injection site. Responses to intradermal injections of histamine and capsaicin were compared in STT neurons recorded in either the superficial or the deep dorsal horn of the anesthetized monkey. Each neuron was identified by antidromic activation from the ventral posterior lateral nucleus of thalamus and classified by its initial responses to mechanical stimuli as wide dynamic range (WDR) or high-threshold (HT). Approximately half of the WDRs and one of the HTs responded weakly to histamine, some with a duration > 5 min, the maximal time allotted. WDRs but not HTs exhibited a significant increase in response to punctate stimulation after histamine consistent with their possible role in mediating histamine-induced hyperalgesia. Neither type of neuron exhibited significant changes in response to stroking, consistent with their unlikely role in mediating alloknesis. Furthermore, nearly all STT neurons exhibited vigorous and persistent responses to capsaicin, after which they became sensitized to stroking and to punctate stimulation. We conclude that the STT neurons in our sample are more likely to contribute to pain, allodynia, and hyperalgesia than to itch and alloknesis.
我们研究了机械敏感的脊髓丘脑束（STT）神经元在介导以下方面的作用：1）皮内注射组胺诱发的瘙痒；2）无害抚摸诱发的瘙痒增强感（异常性瘙痒）；3）注射部位周围皮肤点状刺激诱发的疼痛增强（痛觉过敏）。在麻醉猴的浅背角或深背角记录的STT神经元中，比较了对皮内注射组胺和辣椒素的反应。每个神经元通过丘脑腹后外侧核的逆向激活来识别，并根据其对机械刺激的初始反应分为广动力范围（WDR）或高阈值（HT）。大约一半的WDR神经元和一个HT神经元对组胺反应较弱，有些持续时间>5分钟，这是规定的最长时间。组胺注射后，WDR神经元对点状刺激的反应显著增加，而HT神经元则没有，这与它们在介导组胺诱导的痛觉过敏中可能发挥的作用一致。两种类型的神经元对抚摸的反应均未表现出显著变化，这与它们在介导异常性瘙痒中不太可能发挥作用一致。此外，几乎所有的STT神经元对辣椒素都表现出强烈而持久的反应，之后它们对抚摸和点状刺激变得敏感。我们得出结论，我们样本中的STT神经元更有可能导致疼痛、痛觉过敏和触觉异常，而不是瘙痒和异常性瘙痒。
