PAG电刺激和微注射吗啡对脊髓WDR和NS神经元放电的影响

中脑导水管周围灰质 (PAG)电刺激和微注射吗啡均能显著抑制广动力型 (WDR)和特殊伤害感受 (NS)神经元的伤害感受性放电。但是对 NS神经元放电的抑制明显地大于对 WDR神经元。电刺激 PAG能完全抑制 NS神经元的伤害感受性放电。于 PAG微注射吗啡后 ,NS神经元和 WDR神经元的伤害感受性放电均显著减少。但 NS神经元受抑制的程度更大。电刺激 PAG能使外周传入诱发的背根电位 (DPR)慢电位 (DR- 波 )明显增大 (P <0 .0 0 1)。本研究结果揭示 ,PAG对脊髓 WDR和 NS神经元活动的抑制作用的程度 ,具有明显的差异性 ,以对 NS神经元的抑制为著。由观察 DRP的结果提示 ,在 PAG对脊髓伤害感受神经元的下行抑制作用中 ,可能有突触前抑制参与。

The effects of periaqueductal gray stimuli on WDR and NS neurons in t he dorsal horn of rat spinal cord

Objective:In order to clarify the different reaction of WDR and NS neuronal activies to the stimuli of periaqueductal gray(PAG) and to elucidate the synaptic mechanism in spinal cord level.Methods:The inhibition of the morphine microinjection and the electric stimulation of PAG on the evoked neuronal discharges of WDR and NS units were investigated.In this study, the peripheral afferent evoked dorsal root potential(DRP) was used as the presynapitc inhibitory index to identify the active property of PAG.Results: The peripheral afferent evoked responeses of the both WDR and NS units were markedly suppressed by the electric stimulation of PAG, and this inhibitory effect on NS units was very complete.The scales of inhibition of the firing rate on NS units by PAG morphine microinjection was significantly greater than that of WDR.The result of DRP tested was that DRP slow wave was obviously intensified by the electric stiumlation of PAG(P<0.001).Conclusion:The degree of inhibitory effect of WDR and NS neurons in the stimuli of PAG was different.This study suggests that the descending inhibitory system from PAG may involve presynaptic inhibition in the effect of PAG on the WDR and NS neurons.