下丘脑弓状核注射神经降压素的镇痛效应及机制探讨

STUDY ON THE MECHANISM OF THE ANTINOCICEPTION OF HYPOTHALAMIC ARCUATE NUCLEUS INDUCED BY INJECTION OF NEUROTENSIN IN THE RAT

采用微量注射法,对37只大鼠进行了实验观察.结果如下:①下丘脑弓状核(ARC)注射神经降压素(NT)可使甩尾反应潜伏期(TFL)或痛阈显著升高.对照组注射生理盐水,TFL无明显变化.②ARC先注射纳洛酮,再注射NT,TFL变化值与单纯注射NT组相比明显下降.③ARC注射β-内啡肽(β-End)抗血清,再注射NT,TFL显著下降.④ARC注射生理盐水不影响注射NT的镇痛效应.上述结果表明,大鼠ARC注射NT可产生明显的镇痛效应,该效应可被ARC预先注射纳洛酮或β-内啡肽抗血清翻转,提示NT在ARC的镇痛作用,部分是由β-End介导的.

Neurotensin (NT) was microinjected to evaluate its effect on nociception as well as the possible interaction between NT and endogenous opiate-like substances at the hypothalamic arcuate nucleus(ARC) of the rat. The results were as follows: ① Microinjection of NT(1μg in 1μl) into the ARC resulted in a significant increase in the tail-flick latency (TFL) or pain threshold. In the control group, microinjection of normal saline 2μl showed no significant effect on TFL. ② The effect of NT microinjection was obviously decreased by pretreatment with naloxone (0.2μg in 1μl ) which was injected into ARC 10min beforethe NT injection. ③ Similarly, a prior microinjection of β-endorphin antiserum 1μl into the ARC could sharply reduce the effect of NT microinjected alone. ④ In control experiments, microinjection of saline 2μl into the ARC had no effect on the antinociception action of NT microinjection. These results suggest that ARC injection of NT produced analgesic effect in the rat. This analgesic effect was antagonized by ARC injection of opioid antagonist naloxone or β-endorphin antiserum, but not by normal saline. It is thus likely that the antiuociceptive effects induced by ARC administered neurotensin is mediated, at least partly, by β-endorphin in the ARC of the rat.