阿托品对褪黑素抑制猫丘脑后核群诱发放电的影响

目的研究M受体阻断剂阿托品对褪黑素(melatonin,MT)中枢镇痛作用的影响,进一步探索MT的作用机制。方法采用猫脑立体定位技术和玻璃微电极细胞外记录法,以刺激内脏大神经(GSN)诱发猫丘脑后核群(PO)单位放电为内脏痛指标,侧脑室给药,观察药效。结果0.1% MT(10 μg·kg^-1,icv)可明显抑制刺激GSN在PO诱发的单位放电,0.1%阿托品(20 μg,icv)可拮抗其对PO短潜伏期(58±22) ms诱发放电的抑制作用,而0.1%吗啡(5 μg,icv)对此潜伏期放电的抑制作用则不被等量的阿托品拮抗。结论MT有中枢镇痛作用,在此过程中可能有胆碱能神经的参与,MT的镇痛机制与吗啡存在着差异。

Effect of atropine on the inhibition of melatonin to the unit discharges evoked in the posterior group of thalamic nuclei in cats

AIM: To study the effect of atropine, muscarinic cholinergic antagonist, on the central analgesic action of melatonin (MT) and to explore the mechanism of MT analgesia. METHODS: As an indicator of visceral pain, the unit discharges of the neurons in the posterior group of thalamic nuclei (PO) were caused by stimulating the great splanchnic nerve (GSN) of the cat. The cranial stereotaxic and extracellular glass microelectrode record technique were used. The drugs were given through the intra-cranial-ventricle (icv). RESULTS: 0.1% MT (10 micrograms.kg-1, icv) was shown to inhibit the unit discharge of the neurons in PO of the cat, whether the long latency or the short latency, which was evoked by stimulating GSN. The inhibition of 0.1% MT (10 micrograms.kg-1, icv) on the short latency discharge of neurons in PO was antagonized by 0.1% atropine (20 micrograms, icv). However, 0.1% atropine (20 micrograms, icv) did not show antagonistic effect on the inhibition of 0.1% morphine (5 micrograms, icv) at the same latency. CONCLUSION: MT exhibited central analgesic action with mechanism different from morphine. It was suggested that the cholinergic system may be involved in analgesic process of MT.