据文献报道

脑刺激和吗啡镇痛均依赖于下行性5-羟色胺(5-HT)能通路的完整性。含有大量下行5-HT能神经元的中缝大核(NRM)

正是这一通路的重要发源地。电针可激活NRM而镇痛

也能使中缝核区5-HT和它的主要代谢产物5-羟吲哚乙酸含量升高

NRM内5-HT能胞体荧光增强。减少中枢5-HT可相应减弱或消除电针镇痛效应[11～15]。那么电针激活NRM是否为5-HT能神经元机能活动的增强?为此

本工作在以往观察到电针对NRM神经元具有激活作用In our previous work most NRM neurons could be activated by electro- acupuncture (EA) and its effect could be partially blocked by iontopho- retic naloxone

suggesting that the activation of NRM may be mediated by endogenous opiate-like substance (OLS) released by EA. In the present study

according to the principle of the presynaptic negative feedback regulation the effect of iontophoretic 5-hydroxytryptamine (5-HT) on the neuronal activities in NRM was observed to further explore whether these activated neurons were serotonergic. The experiments were carried out on male adult rats under slight ure- thane anaesthesia. The unit activity was extracellularly recorded with the central tube of the multipipettes filled with 4 M NaCl. Most neurons in NRM (17 out of 27

63%) responded to iontophoretic 5-HT with decreasing firing rate; only one neuron responded with increasing firing rate; and the remainder (9 of 27) had no change. Among 14 neurons activated by EA

12 neurons were inhibited by ionto- phoretic 5-HT and all the neurons in which the nociceptive responses were inhibited by EA could be inhibited by iontophoretic 5-HT. Moreover

7 out of 8 neurons in which the acupuncture inhibitory effect could be reversed by iontophoretic naloxone could also be inhibited by iontophoretic 5-HT. In addition

both 17 neurons inhibited by 5-HT and all 10 neurons which were antidromatically activated by the stimulation of dorsal lateral fascicular could be excited by noxious stimulation

classified as excitatory neurons. The above results suggested that most excitatory neurons activated by OLS released by EA might be considered as the serotonergic raphe-spinal neurons

which plays an important role in acupuncture analgesia.