Experimental study on mechanism of pain control in hypothalamo-brain-stem system

用微量注射法和热板式镇痛仪研究了大鼠下丘脑-脑干系统的痛觉控制机制，特别是在吗啡镇痛中的作用。将注射管立体定向插入大鼠下丘脑室旁核(PVN)。术后第5~7天，注射吗啡7 mg，测定痛阈值(热板上爪子舔潜伏期52.0sy+-0.1ﾟC)。微量注射吗啡的大鼠疼痛敏感性显著降低。结论：1.室旁核是吗啡作用的明确部位。研究了纳洛酮对下丘脑室旁核疼痛控制机制的影响。大鼠腹腔注射纳洛酮后，下丘脑室旁核内吗啡的镇痛作用呈中度下降。在中脑导水管周围灰质微量注射吗啡和纳洛酮的大鼠中也观察到了这两种作用。这些大鼠表现出与PVN组相似的镇痛模式。这些结果提示，PVN可能是下丘脑-脑干系统控制疼痛的重要部位。室旁核似乎也是脑干下行疼痛控制系统的初始位置，一直延伸到脊髓。

The mechanism of pain control in hypothalamo-brain stem system was investigated in rats by way of the microinjection method and a hot-plate analgesia meter, being with special reference to the role of the in morphine analgesia.1. An injection cannula was stereotactically inserted into the paraventricular nucleus(PVN) of hypothalamus of rats. On the 5-7th postoperative day, morphine(7mug) was injected and the pain threshold(paw lick latency on the hot-plate, 52.0(〕SY.+-.〔)0.1ﾟC) was measured. Morphine microinjected rats disclosed marked diminution of pain susceptibity. PVN is a definite site of morphine action.2. The effect of naloxone was also studied as for the mechanism of pain control of PVN.Rats which was administered intraperitoneally naloxone, showed moderate decrease of the analgesic effect of morphine administration into the PVN.3. Both effects of morphine and naloxone were also measured in the rats morphine microinjected into the periaqueductal gray matter. These rats showed the similar patern of analgesia of PVN groups.4. These findings suggested that PVN appeared to be the important site in control of pain in hypothalamo-brain stem system. And PVN also appears to be the initial site of descending pain control system in the brain stem down to the spinal cord.