Ying S W, Huang Z Q
Department of Biomedical Sciences, McMaster University, Ontario, Canada.
Zhongguo Yao Li Xue Bao. 1990 Sep;11(5):411-4.
Sensitivity to painful stimuli was measured by hot plate, writhing tests and electric caudal stimulation in mice. The mice were kept under light-dark 12/12 cycle with light out at 18:00 for at least 2 wk. Both basal analgesia and meperidine (pethidine)-induced analgesic effect exhibited parallel circadian rhythms, with the marked peak and through occurring at mid-dark and mid-light phases, respectively. The day-night differences in pain threshold 10 d after pinealectomy were not evident, especially in the loss of dark time augmentation of analgesic responses, but persisted in sham operated mice. Melatonin (MT) 50-200 mg/kg ip during light phase produced analgesic activity. MT 250 mg/kg ip resulted in a loss of the righting reflex. In pinealectomized mice, the pre-treatment of MT 5 mg/kg potentiated levels of analgesia induced by meperidine 10 mg/kg or morphine 5 mg/kg. It is possible that MT is one of the endogenous nocifensor inhibitors in CNS.
通过热板法、扭体试验和电刺激小鼠尾部来测量对疼痛刺激的敏感性。小鼠饲养在12小时光照/12小时黑暗周期下，18:00熄灯，至少饲养2周。基础镇痛和哌替啶（度冷丁）诱导的镇痛作用均呈现平行的昼夜节律，显著峰值和谷值分别出现在黑暗中期和光照中期。松果体切除术后10天，疼痛阈值的昼夜差异不明显，尤其是在镇痛反应的暗时增强丧失方面，但在假手术小鼠中持续存在。褪黑素（MT）在光照期腹腔注射50 - 200 mg/kg产生镇痛活性。MT腹腔注射250 mg/kg导致翻正反射消失。在松果体切除的小鼠中，预先给予5 mg/kg的MT可增强10 mg/kg哌替啶或5 mg/kg吗啡诱导的镇痛水平。MT有可能是中枢神经系统内源性伤害感受抑制剂之一。
