近年来镇痛原理研究的大量工作证明

中枢神经系统中存在着内源性痛觉调制系统

各种镇痛措施如脑刺激镇痛、针刺镇痛、吗啡镇痛等作用方式和途径虽不相同

但本质上可能都是激活了内源性痛觉调制系统而发挥镇痛效应的。我们研究室以往的(1)Electroacupuncture and electrical stimulation of hypothalamic arcuate nucleus(ARC)of rats had a marked inhibitory effect on the pain discharges of cells evoked by peripheral noxious stimuli in parafascicular nucleus (PF)of thalamus. (2)The inhibitory effect of both electroacupuncture and ARC stimulation disappeared after intraperitoneal injection of PCPA(tryptophan hydroxylase inhibitor). (3)Electrolytic lesion of dorsal raphe nucleus(DR)markedly reversed the inhibitory effect of both electroacupuncture and ARC stimulation on pain evoked unit discharges of PF.Electrolytic lesion of nucleus raphe magnus (NRM)markedly reversed the effect of electroacupuncture

but had no ma- rked influence on the effect of ARC stimulation. (4)It is suggested that there might exist in endogenous pain modulation system two distinct pain-inhibitory pathways

i.e.

the desending and asce- nding pain-inhibitory pathways

the former blocks the transmission of noxio- us message at the spinal cord levels

and the latter modifies the responses to pain at the higher CNS levels.