摘除垂体对大鼠脑内5-羟色胺、去甲肾上腺素及针刺镇痛的影响

<正> 从往的实验表明,大鼠摘除垂体后,针刺镇痛效应明显减弱;摘除垂体后注射促肾上腺皮质激素(ACTH),针刺镇痛效应得到恢复。并认为ACTH恢复针刺镇痛效应的作用与皮质酮无关,从而提示,ACTH在针刺镇痛过程中可能具有中枢作用。因针刺镇痛与脑内5-羟色胺(5-HT)神经元及去甲肾上腺素(NE)神经元的神经传递密切相关,所以,进一步阐明垂体在针刺镇痛中的作用机制,显然是有意义的。本文采用摘除大鼠垂体的方法,观察对脑内5-

THE EFFECTS OF HYPOPHYSECTOMY ON BRAIN 5--HYDROXYTRYPTAMINE AND NOREPINEPHRINE AND ACUPUNCTURE ANALGESIA IN RAT

There are a lot of evidences that brain 5-hydroxytryptamine (5-HT) and norepinephrine (NE) are concerned with acupuncture analgesia. The previous works suggested that the cause of decreased acupuncture analge- sa in hypophysectomized rats was probably due to the defect of central actions of pituitary ACTH. In this paper, we observed the effects of hypo- physectomy on the 5-HT, NE in the brain and acupuncture analgesia in rats. The interaction among ACTH, 5-HT and NE in acupuncture analge- sia had been further studied. Electroacupuncture was applied to the "Renzhong" and "Chengjiang" points. The pain threshold was measured with radiantheat tail-flick me- thod. Analgesic effects was expressed as the percentage of increase in the pain threshold after electroacupuncture. The brain content of 5-HT, 5-hy- droxyindoleacetic acid (5-HIAA) and NE was determined with fluorescence spectrophotometry. In 15～30 days after hypophysectomy, the baseline pain threshold increased markedly. Brain 5-HIAA levels increased by 28% (p<0.05), as compared with those of the control group. In hypophysectomized rats the acupuncture analgesic effect was only 13.07±10.62%, much less than that (58.51±10.6%) of the electroacupu- ncture control group and sham operation group (p<0.05). There was no marked increase in the brain 5-HT levels and its turnover rate, no ma- rked decrease in the brain NE levels, as compared with those of the ele- ctroacupuncture control group and sham operation group. After hypophyse- ctomized rats were given ACTH intraperitoneally (15 units/kg), the reco- very of acupuncture analgesic effect ensued, and the brain 5-HT levels and its turnover rate also increased markedly. The above results demonstrate that in the process of acupuncture ana- lgesia the central actions of ACTH, probably to some extent, are achieved by means of strengthening the activity of central 5-HT system.