刺激PAG对C纤维传入诱发皮层电反应的影响

EFFECT OF STIMULATING MIDBRAIN PERIAQUEDUCTAL GRAY ON THE ELECTRICAL RESPONSE OF SOMATOSENSORY CORTEX TO C-FIBER INPUT IN CATS

电刺激中脑导水管周围灰质(Periaqueductal Gray,PAG)对 C 类纤维传入引起的体感皮层诱发电位(C-CEP)和脊髓背表面电位(C-SSP)均有明显的抑制作用,对前者的作用更大。在脊髓背表面滴加赛庚啶后,刺激 PAG 对 C-SSP 的抑制变得不明显,表明 PAG下行抑制通路被阻断;但刺激 PAG 对 C-CEP 抑制仍明显,仅稍减小。提示 PAG 除了通过下行通路以外,可能还通过上行通路抑制 C-CEP。在脊髓背表面滴加赛庚啶后,静脉注射纳洛酮和赛庚啶可明显减弱电刺激 PAG 对 C-CEP 的抑制作用,提示内源性阿片样物质和5-羟色胺可能是上行抑制通路中主要的神经递质。

The electrical responses of the somatosensory cortex(C-CEP)and spinal cord(C-SSP)to C-fiber inputs could be markedly inhibited by stimulating the periaquedu-ctal gray(PAG),and the inhibition on C-CEP was greater than that on C-SSP.After application of cyproheptadine on the dorsal surface of the spinal cord,PAGstimulation could still inhibit C-CEP,but not C-SSP.It was suggested that PAGmight inhibit C-CEP through ascending as well as descending pathways.Afterblocking the descending inhibitory pathway by cyproheptadine i.v.injection,cy-proheptadine and naloxone could antagonize the inhibitory effect of PAG stimula-tion on C-CEP,indicating that endogenous opiate-like substance and serotoninmight play an important role in the transmission of the ascending inhibitory path-ways from PAG.