Pertovaara A, Kontinen V K, Kalso E A
Department of Physiology, University of Helsinki, Finland.
Exp Neurol. 1997 Oct;147(2):428-36. doi: 10.1006/exnr.1997.6555.
We studied whether a chronic neuropathy induced by unilateral spinal nerve ligation changes the response characteristics of spinal dorsal horn wide-dynamic range (WDR) neurons or their periaqueductal gray (PAG)-induced descending modulation. Experiments were performed in rats with behaviorally demonstrated allodynia induced by spinal nerve ligation and in a group of nonneuropathic control rats. The stimulus-response functions of WDR neurons for mechanical and thermal stimuli and the modulation of their peripherally evoked responses by electrical stimulation of the PAG were determined under pentobarbital anesthesia. The results showed that neuropathy caused a significant leftward shift in stimulus-response functions for mechanical stimuli. In contrast, stimulus-response functions for noxious heat stimuli in the neuropathic limb were, if anything, shifted rightward, although this shift was short of statistical significance. In neuropathic rats, PAG stimulation produced a significantly stronger attenuation of spinal neuronal responses induced by noxious heat in the unoperated than in the operated side. At the intensity that produced attenuation of noxious heat stimuli, PAG stimulation did not produce any significant change in spinal neuronal responses evoked by mechanical stimuli either from the operated or the nonoperated hindlimb of the neuropathic rats. Spontaneous activity of WDR neurons was higher in the operated side of neuropathic rats than in control rats. Afterdischarges evoked by peripheral stimuli were observed in 1/16 of the WDR neurons ipsilateral to spinal nerve ligation and not at all in other experimental groups. The WDR neurons studied were not activated by innocuous or noxious cold stimuli. The results indicate that spinal nerve ligation induces increased spontaneous activity and enhanced responses to mechanical stimuli in the spinal dorsal horn WDR neurons, whereas noxious heat-evoked responses are not significantly changed or if anything, attenuated. Moreover, the inhibition of noxious heat stimuli by PAG stimulation is attenuated in the neuropathic side. It is proposed that the observed changes in the response characteristics of the spinal dorsal horn WDR neurons and in their descending modulation may contribute to the neuropathic symptoms in these animals.
我们研究了单侧脊神经结扎诱导的慢性神经病变是否会改变脊髓背角广动力范围（WDR）神经元的反应特性或其导水管周围灰质（PAG）诱导的下行调制。实验在行为上表现出由脊神经结扎诱导的异常性疼痛的大鼠以及一组非神经病变对照大鼠中进行。在戊巴比妥麻醉下，测定WDR神经元对机械和热刺激的刺激 - 反应函数以及通过PAG电刺激对其外周诱发反应的调制。结果表明，神经病变导致机械刺激的刺激 - 反应函数显著向左移位。相比之下，神经病变肢体中有害热刺激的刺激 - 反应函数即使有变化，也向右移位，尽管这种移位缺乏统计学意义。在神经病变大鼠中，PAG刺激在未手术侧比手术侧产生的有害热诱导的脊髓神经元反应的衰减明显更强。在产生有害热刺激衰减的强度下，PAG刺激在神经病变大鼠的手术或未手术后肢诱发的机械刺激所引起的脊髓神经元反应中均未产生任何显著变化。神经病变大鼠手术侧WDR神经元的自发活动高于对照大鼠。在与脊神经结扎同侧的WDR神经元中，1/16观察到外周刺激诱发的后放电，而在其他实验组中未观察到。所研究的WDR神经元未被无害或有害冷刺激激活。结果表明，脊神经结扎诱导脊髓背角WDR神经元的自发活动增加和对机械刺激的反应增强，而有害热诱发反应没有显著变化，或者如果有变化的话，是减弱的。此外，PAG刺激对有害热刺激的抑制在神经病变侧减弱。有人提出，脊髓背角WDR神经元反应特性及其下行调制的观察到的变化可能导致这些动物的神经病变症状。
