Experimental study on mechanism of pain control in hypothalamo-pituitary system

本实验用微量注射法和热板法研究了大鼠下丘脑-垂体系统的镇痛机制，特别是下丘脑室旁核（PVN）在吗啡依赖中的作用.将注射套管立体定向插入6组34只正常和垂体切除大鼠的PVN。术后第5- 7天，注射吗啡（7 μ g），并测定痛阈（热板上舔爪潜伏期，52.0 ± 0.01）。p）0.1 ℃）。16只大鼠注射吗啡后疼痛敏感性明显降低。PVN是吗啡作用的明确部位.同时观察垂体切除对PVN疼痛控制的作用。吗啡对去垂体大鼠的镇痛作用有轻度增强作用.在10只大鼠的PVN内分别微量注射促肾上腺皮质激素释放因子（CRF）和生理盐水。在这些实验中，测定了以下4组大鼠的痛阈：切除垂体和不切除垂体的CRF或生理盐水注射组。虽然PVN是下丘脑-垂体系统控制疼痛的重要部位，但PVN内微量注射CRF无论是否切除垂体均不能减轻疼痛，提示PVN是下丘脑-垂体系统控制疼痛的重要部位。但CRF和垂体在这种疼痛控制机制中并不起重要作用。

The mechanism of pain control in hypothalamo-pituitary 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 paraventricular nucieus(PVN) of hypothalamus in morphine analgesia.1. An injection cannula was stereotactically inserted into the PVN of 34 normal and hypophysectomized rats of 6 groups. On the 5-7th postoperative day, morphine (7mug) was injected and the pain threshold (paw lick latency on the hot-plate, 52.0(]SY.+-. p)0.1ﾟC) was measured. Morphine microinjected 16 rats disclosed marked diminution of pain susceptibility. PVN is a definite site of morphine action.2. The effect of hypophysectomy was also studied in the role of pain control of PVN. Morphine administration in the hypophysectomized rats showed mild reinforces the analgesic effect.3. Corticotropin releasing factor (CRF) and saline solution were also micro-injected into the PVN of 10 rats, respectively In these experiments the pain threshold was measured in the following 4 groups, namely in the CRF or saline injected groups with hypophysectomy and non-hypophysectomy. Although PVN appears to be the important site in control of pain relief in hypothalamo-pituitary system, the microinjection of CRF into the PVN with or without hypophysectomy didn't produce the diminution in pain.In summary, these findings suggested that PVN appeared to be the important site in control of pain in hypothalamopituitary system. However, CRF and pituitary gland did not play the important role in the mechanism of this type of pain control.