在中枢神经系统内

内源性阿片样物质的镇痛作用引起了人们的广泛注意。如果阿片样物质对痛觉具有调制作用

则阿片受体阻断剂纳洛酮应能改变正常动物的痛感受或痛反应。许多人试图通过纳洛酮的处理来揭露对伤害性刺激的传递或反应是否存在紧张性调控作用

可惜现有的一些研究资料仍存在许多相互矛盾的地方。有人证明外源性阿片样物质可抑制一些Experiments were done in 25 rabbits.Glass microelectrodes were usedto record the discharges of nociceptive neurons in the nucleus parafascicu-laris of thalamus.It was found that intraventricular or intravenous injec-tion of naloxone could facilitate selectively the nociceptive discharges inparafascicular nucleus without any effect on the activity of non-nociceptiveneurons.In addition

naloxone could have reversal of the inhibitory effectof morphine on the nociceptive discharges.From the results of the presentstudy it seems to suggest that the endogenous opiate-like substances probablyhavea tonic regulatory role on the transmission of the pain impulses in th-alamus.