大鼠脑内P物质在针刺镇痛中的作用及其与脑啡肽的关系

THE ROIE OF SUBSTANCE P IN ELECTROACUPUNCTURE ANALGESIA AND ITS RELATION TO ENKEPHLINS IN THE RAT BRAIN

P物质(SP)在痛觉感受方面已有不少研究。多数学者认为,在脊髓水平它是传递痛信息的神经递质;而在中脑导水管周围灰质(PAG)或脑室注射SP则出现镇痛作用。因此。

In order to understand the role of substance P (SP) in the brain and the relationship between SP and enkephalins in the electroacupuncture analgesia (EA), we have observed the influence of SP-antagonist, (D-Arg', D-Phe^5, D-Trp^(7.9), Leu^(11))-SP (DADPDTL) injected intracerebroventricularly (icv) on EA and the change of the level of SP in the brain regions of the rat durinf EA. We have made a further observations on the influences of the naloxone (NX) on the che change of the content of SP induced by EA and DADPDTL on the increase in Leu-enkephalins (LEK) induced by EA. The Wistar rats were used in the experiment. The latency of the tail flick, immersing the tip of rat tail (4cm) into hot-water of 50℃, was taken as the pain threshold. The drugs were injected icv via plastic cannulae implanted in the bilateral ventricles. The EA was applied to the point of 'Zusanli' (S36). The contents of SP and LEK were determined radioimmunoassay in the hypothalamus, mid-brain, striatum and pons-meduila-oblongata. The pain threshold was increased by 48±9% (P<0.01) after EA. But icv injection of DADPDTL decreased the pain threshold by 14±7% after EA. The result suggests that DADPDTL can antagonize the effect of EA and that SP in the brain is involved in EA. After EA the contents of SP in the hypothalamus and mid-brain of the rats were decreased by 29% and 28% in comparison with that of the control group respectively (both of them, P<0.05), but the contents of SP in the striatum and pons-medulla-oblongata had no significant change. It indicates that EA can decrease the levels of SP in the hypothalamus and mid-brain of rats. In NX (20ug) injected icv plus EA group, the effect of EA might be blocked partially (the pain threshold increased only by 20±12% after EA, P>0.05), while the levels of SP in the hypothalamus and mid-brain were higher than simple EA group, but not different to that of control group. The result shows that NX administered icv can inhibit the decrease of SP in the brain induced by EA. While DADPDTL blocked the effect of EA, the levels of LEK in the hypothalamus and mid-brain did not have significant difference with that of simple EA group, but it was higher than that of control group. The result shows that DADPDTL cannot change the increase on LEK in the brain induced by EA. As mentioned above, endogenous SP in the brain is involved in the EA. The relationship system is first activated by EA and in turn, the enkephalin accelerates the release of SP to be involved in analgesia.