近年来研究表明

发源于中脑导水管周围灰质(PAG)的脑干下行抑制系统

在吗啡镇痛、脑刺激镇痛中具有十分重要的作用。延脑中缝大核(NRM)是该系统换元传递的枢纽。国外一些学者设想

下行抑制系统中PAG到NRM的下行通路可能是由吗啡类物质调制的。这一观点在我们以往的工作中得到了初步证实。我们观察到

电针对NRM神经元的激活效应可被局部导入吗啡拮抗纳洛酮所阻断。那么

在NRM直接微电泳导入脑啡肽和吗啡

是In our Previous work

the activation of neuronal activities of nucleus raphe magnus (NRN) by acupunture could be blocked by iontophoretic nal- oxone

suggesting that the endogenous opiate-like substance (OLS) may play an important role in activating NRN neurons by acupuncture

In pre- sent study

The effect of acupuncture was compared with that of iontoph- oretic leucine-enkephalin

so as to further investigate the enkephalinergic mechanism of the activation of NRN neurons by acupuncture. The experiments were carried out on adult male rats under slight uret- han anaesthesia. Unit activities were extracellularly recorded with central tube of the multi-pippetes filled with 4 M Nacl and neuronal responses to acupuncture and iontophoretic enkephalin were observed. Among 11 neurons

the firing rate of 8 neurons (73%) was increased by acupuncture applied on "Zusanli" Points

only that of one neuron was dec- reased and the remaining 2 neurons showed no change. When leucine-enk- ephalin was iontophoretically ejected near the cell body of the NRN neu- rons

the firing rate was increased in most neurons (14 of 21 neurons

67%)

decreased only in one neuron

and the remainder had no Change. The effect of iontophoretic enkephalin was quite similar to that of acupuncture

only that the occurene of the exciting effect of acupuncture required a longer period of time. Bcth of their exciting effects could be blocked by iontoph- oretic naloxone. In addition

the effect of iontophoretic morphine was observed. Only in 50% neurons the firing rate was increased and the magnitude of the ac- tion was less than that of acupuncture and iontophoretic enkephalin. These results further support that the OLS released by acupuncture may mediate the activation of NRN neurons and it may play an important role in acupuncture analgesia.