Relative effectiveness of C primary afferent fibers of different origins in evoking a prolonged facilitation of the flexor reflex in the rat
Relative effectiveness of C primary afferent fibers of different origins in evoking a prolonged facilitation of the flexor reflex in the rat
复制标题
不同来源的 C 初级传入纤维在引起大鼠屈肌反射的长期促进方面的相对有效性
作者：
C. Woolf;P. Wall
对不同来源的c -传入纤维施加条件刺激所产生的腘绳肌屈肌退缩反射兴奋性的变化进行了研究。在没有条件刺激的情况下，通过对脚趾的标准阈上机械刺激引起的屈肌反射在重复测试数小时后是稳定的。三种类型的条件反射刺激被用来试图改变屈肌反射的兴奋性；电刺激皮肤（腓肠）神经或肌肉（腓肠肌-比目鱼）神经的c纤维强度；芥菜油是一种化学刺激物，可激活化学敏感的C-神经传入，应用于皮肤或注射于肌肉和关节内；胫骨肌融合强直性收缩间接激活高阈值肌肉传入神经。足以激活c -传入纤维的强度条件刺激导致屈肌运动神经元对标准测试输入的异突触促进反应，持续时间从3分钟到3小时以上，取决于刺激和激活的c -传入纤维。用c纤维神经毒素辣椒素预处理坐骨神经可消除所有条件反射后的促进作用，这表明可能是c传入神经主要负责条件反射刺激的促进作用，尽管一些A δ传入神经可能起作用。辣椒素预处理不改变对测试刺激的反射反应。关节内注射5微升芥菜油后，屈肌反射兴奋性的延长时间最长。使用随后的利多卡因关节内注射，发现反射的延长促进是由条件反射刺激产生的传入输入触发的，不需要持续的输入来维持。这些结果表明，由于不同来源的c -纤维的激活，脊髓刺激反应关系中存在一系列中枢变化。其中一些变化持续时间的延长意味着c传入的外周激活将改变脊髓对其他条件输入的功能反应，这可能是外周组织损伤后发现的一些感觉和运动改变的原因。
Changes in the excitability of the hamstring flexor withdrawal reflex produced by conditioning stimuli applied to C-afferent fibers of different origins have been examined in the decerebrate spinal rat. In the absence of conditioning stimuli, the flexor reflex elicited by a standard suprathreshold mechanical stimulus to the toes is stable when tested repeatedly for hours. Three categories of conditioning stimuli have been used in an attempt to modify the excitability of the flexor reflex; electrical stimulation of a cutaneous (sural) nerve or a muscle (gastrocnemius-soleus) nerve at C-fiber strength; the application of mustard oil, a chemical irritant that activates chemosensitive C- afferents, to the skin or injected intramuscularly and intraarticularly; and the indirect activation of high-threshold muscle afferents by fused tetanic contractions of the tibial muscles. Conditioning stimuli of an intensity sufficient to activate C-afferent fibers result in a heterosynaptic facilitation of the flexor motoneuronal response to the standard test input, which lasts from 3 min to more than 3 hr, depending on the stimulus and the C-afferents activated. Pretreatment of the sciatic nerve with the C-fiber neurotoxin capsaicin abolishes all the postconditioning facilitations, which is an indication that it is likely that it is C-afferents that are primarily responsible for the facilitatory effects of the conditioning stimuli, although some A delta afferents may contribute. Capsaicin pretreatment does not modify the reflex response to the test stimulus. The most prolonged increase in the excitability of the flexor reflex resulted from intraarticular injections of 5 microliter mustard oil. Using the subsequent injection of lignocaine intraarticulary, it was found that the prolonged facilitation of the reflex is triggered by the afferent input generated by the conditioning stimulus and does not require an ongoing input for its maintenance. These results indicate that there is a spectrum of central changes in the stimulus response relations of the spinal cord resulting from the activation of C-fibers of different origins. The prolonged duration of some of these changes means that the peripheral activation of C-afferents will modify the functional response of the spinal cord to other inputs applied long after the conditioning input, and this may be responsible for some ofthe sensory and motor alterations found after peripheral tissue injury.