导水管周围灰质(PAG)、中缝大核(NRM)、脊髓下行抑制系统在针刺镇痛中的作用已为许多生理研究所证实

电针刺激可能通过激活PAG和NRM不同的神经递质系统而发挥镇痛作用。形态学研究揭示PAG腹外侧部和NRM不仅含有多种生物胺类、肽类和乙酰胆碱神经元和纤12 Wistar rats(220-250g)were divided into control and experimental groups.Pain threshold was determined by WQ-gE Pain Threshold Measuring Apparatus.EA was applied at bilateral"Zusanli"points.The animals showing EA analgesia and the control animals were sacrificed and the ventrolateral part of PAG and the NRM were taken out for electron microscopic observation. The peripheral region of ventrolateral PAG(PAG-PR)aud the NRM contained a wide variety of cell types and synaptic relationships.The neurons and axo-dendritic synapses of the PAG-PR and NRM were analysed in EA and control groups.In EA analgesia group

the clear round vesicle-containing presynaptic boutons and the presynaptic bouton with clear round vesicles and granular vesicles showed a significant decrease of their vesicle content.Part of the mitochondria and endoplasmic reticulum in the neurons appeared the expanded profiles.These ultrastructural changes of the PAG and the NRM during EA analgesia may indicate an increased release of acetylcholine

biogenic amines and/or pepride neurotransmitters and that the neurons were in active functional state.