褪黑素对七氟醚重复暴露诱发新生大鼠远期认知障碍的影响

Effects of melatonin on long-term cognitive impairments induced by repeated neonatal sevoflurane exposures

目的探讨褪黑素对七氟醚重复暴露诱发新生大鼠远期认知功能障碍的影响及可能机制。方法选择新生雄性SD大鼠96只,6日龄,体重10~15 g。采用随机数字表法将大鼠分为四组:对照组(C组)、褪黑素组(M组)、七氟醚组(S组)和七氟醚+褪黑素组(SM组),每组24只。C组自由饮食饮水;M组在出生后第6天开始每天接受1次腹腔注射褪黑素10 mg/kg,连续3 d,第21天分笼后开始饮用含褪黑素的水;S组在出生后第6天开始每天吸入3%七氟醚2 h,连续3 d;SM组在出生后第6天开始每天接受1次腹腔注射褪黑素10 mg/kg,后吸入3%七氟醚2 h,连续3 d,第21天分笼后开始饮用含褪黑素的水。大鼠出生后第35天采用旷场实验记录探索总路程以及中央格停留时间,第36天采用新物体识别实验记录识别指数;第37—39天采用场景性、条件性恐惧实验记录僵直时间。出生后第8、40天取大鼠脑组织,采用Western blot法检测大鼠前额叶皮层iNOS和CD68蛋白含量,ELISA法检测IL-1β和IL-6浓度。结果与C组比较,S组识别指数明显降低,场景性、条件性恐惧测试阶段僵直时间明显缩短,出生后第8天前额叶皮层iNOS和CD68蛋白含量、IL-1β和IL-6浓度明显升高(P<0.05)。与S组比较,SM组识别指数明显升高,场景性、条件性恐惧测试阶段僵直时间明显延长,出生后第8天前额叶皮层iNOS和CD68蛋白含量、IL-1β和IL-6浓度明显降低(P<0.05)。出生后第40天四组间前额叶皮层iNOS和CD68蛋白含量、IL-1β和IL-6浓度差异无统计学意义。结论褪黑素可以抑制前额叶皮层的炎症反应,改善七氟醚重复暴露导致的新生大鼠远期认知障碍。

Objective To investigate the effects and possible mechanisms of melatonin on long-term cognitive impairments induced by repeated neonatal sevoflurane exposures.Methods Ninety-six neonatal male SD rats at postnatal day 6,weighed 10-15 g,were randomly divided equally into four groups:the control group(group C),the melatonin group(group M),the sevoflurane group(group S),and the sevoflurane+melatonin group(group SM),24 rats in each group.Group C received free food and water.Group M received one intraperitoneal injection of melatonin 10 mg/kg per day for three consecutive days starting on postnatal day 6,and started drinking melatonin-containing water after cage separation on day 21.Group S inhaled 3%sevoflurane for 2 hours per day for three consecutive days starting on postnatal day 6.Group SM received one daily intraperitoneal injection of melatonin 10 mg/kg followed by inhalation of 3%sevoflurane for 2 hours per day for three consecutive days starting on postnatal day 6,and melatonin-containing water was started on postnatal day 21 after cage separation.Open field test was performed on postnatal day 35,novel object recognition was performed on postnatal day 36,and the fear conditioning tests were performed from postnatal day 37 to 39.Rat brain tissues were taken on postnatal day 8 and day 40,the content of iNOS and CD68 protein in the prefrontal cortex was detected by Western blot,and the concentration of IL-6 and IL-1βwas detected by ELISA.Results Compared with group C,the discrimination index was significantly decreased,the freezing time was significantly shortened,the content of iNOS and CD68 protein,and the concentration of IL-6 and IL-1βin the prefrontal cortex were significantly increased on postnatal day 8 in group S(P<0.05).Compared with group S,the discrimination index was significantly increased,the freezing time was significantly prolonged,the content of iNOS and CD68 protein,and the concentration of IL-6 and IL-1βin the prefrontal cortex were significantly decreased on postnatal day 8 in group SM(P<0.05).There were no statistically significant differences in the content of iNOS and CD68 protein,and the concentration of IL-6 and IL-1βin the prefrontal cortex between the four groups on postnatal day 40.Conclusion Melatonin can inhibit the inflammatory response in the prefrontal cortex and improve long-term cognitive impairments in neonatal rats induced by repeated neonatal sevoflurane exposures.