八肽胆囊收缩素对抗吗啡对丘脑束旁核痛反应神经元放电的影响

已知脑室注射硫化八肽胆囊收缩素(CCK-8)对吗啡镇痛效应(用辐射热甩尾反应的潜伏期作测痛指标)有对抗作用。本工作研究了脑室注射CCK-8对吗啡引起的大鼠丘脑两侧束旁核痛反应神经元同时电变化的影响。结果如下:(1)腹腔注射吗啡(10mg/kg)可抑制痛兴奋神经元(PEN)和加强痛抑制神经元(PIN)的电活动。(2)脑室注射CCK-8(15ng/15μl)能对抗吗啡引起PEN放电的抑制作用和PIN电活动的加强作用。无硫CCK-8对吗啡的效应没有对抗作用。(3)注射CCK-8可同时对抗吗啡对束旁核中一个PEN的抑制作用和一个PIN的加强作用。上述结果与甩尾阈测痛的结果一致,即CCK-8对吗啡引起的镇痛效应有明显的对抗作用。

ANTAGONISM TO THE EFFECT OF MORPHINE ON ELECTRIC DISCHARGES OF PAIN--RELATED NEURONS IN NUCLEUS PARAFASCICULARIS OF THALAMUS BY CHOLECYSTOKININ OCTAPEPTIDE

It was reported that the antinociceptive effect of morphine as determined bythe latency of the radiant heat induced tail flick response was antagonized by cholecy-stokinin octapeptide (CCK-8) administered intracerebroventricularly (ICV). Inthe present study the effect of morphine on the electric activities of simultaneouslyrecorded pain-related neurons of nucleus parafascicularis in both sides of the ratbrain were studied after ICV injection of CCK-8. The results were as follows: (1) Intraperitoneal injection of morphine (10mg/kg) resulted in an inhibitionof the evoked response of the pain-excitation neurons (PEN) as well as an excitationof the evoked response of the pain-inhibition neurons (PIN). (2) Both the inhibitory effect of morphine on the electric discharges of PENand the excitatory effect of morphine on the electric activities of PIN were almosteliminated by the ICV administration of CCK-8 at a dose of 15 ng. No signifi-cant effect was observed when unsulfated CCK-8 was used instead of CCK-8. (3) In some of the animals, recordings were made from a PEN and a PINsimultaneously in each side of the nucleus parafascicularis. It was clearly shownthat administration of CCK-8 resulted in a reversal of the effect of morphine, ir-respective of the recorded neuron being PEN or PIN. The results are consistent with the conclusion obtained in the previous studyusing tail flick latency as the endpoint of nociception, i. e., CCK-8 is antagonisticto the antinociceptive effect of morphine.