Zhen Ci Yan Jiu. 1991 ; 16(2): 125-8.

[Effect of intracerebral injection of substance P on serotonin contents of several brain regions and its relation with pain threshold, electroacupuncture analgesia in rats]

Li X, Zhao B, Ruan H, Li H, Liu Z.

Department of Physiology, Third Military Medical College, Chongqing.

The purpose of this study is to observe the effect of intracerebroventricular (icv) and intra-PAG injection of substance P (SP) on serotonin (5-HT) contents of hypothalamus, hippocampus, striatum and its relation with the change of pain threshold, electroacupuncture (EA) analgesia. The results were as follows: (1) After icv injection of SP, the pain threshold and the 5-HT contents of hypothalamus, hippocampus were significantly increased. After depletion of the 5-HT contents in brain by pCPA, the inhibitor of 5-HT synthesis, the effect of SP on elevating pain threshold and the 5-HT contents of hypothalamus, hippocampus were markedly attenuated, bud did not prevent the analgesic effect of SP (2) The pain threshold and the 5-HT contents of hypothalamus, hippocampus were dose-dependently increased by intra-PAG injection of SP. (3) The intra-PAG injection of SP introduced simultaneously with high or low frequency EA did not affect the change of 5-HT contents of three brain regions, but caused a more marked elevation of pain threshold. These results suggest that the serotoninergic system may be activated by PAG for the mediation of SP induced analgesia. There is a synergic action of analgesia between the effects produced by intra-PAG injection of SP and those by high or low frequency EA.