ABSTRACT
Objective:To evaluate the effect of melatonin on prefrontal cortex ischemia-induced cognitive impairment in rats and to investigate the receptor mechanism.Methods:Clean-grade adult male Sprague-Dawley rats, weighing 300 g, were selected, and a catheter was implanted into the prefrontal cortex.The experiment was performed in two parts.Experiment Ⅰ Twenty-four rats, in which catheters were successfully inserted into the prefrontal cortex, were assigned into 3 groups ( n=8 each) using a random number table method: control group (group C), model group (group M) and melatonin group (group ME). Normal saline 0.5 μl was injected into the prefrontal cortex in group C, 1 μmol/L endothelin 0.5 μl was microinjected into the prefrontal cortex in group M, and 1 μmol/L endothelin and 1 μmol/L melatonin 0.5 μl were injected into the prefrontal cortex in group ME.Experiment Ⅱ Forty-four rats, in which catheters were successfully inserted into the prefrontal cortex, were assigned into 4 groups ( n=11 each) using a random number table method: model group (group M), melatonin group (group ME), MT 1/2R antagonist luzindole + melatonin group (group L + ME) and MT 2R antagonist 4p-pdot + melatonin group (group P + ME). In group M, 1 μmol/l endothelin 0.5 μl was microinjected into the prefrontal cortex.In group ME, 1 μmol/L endothelin + 1 μmol/L melatonin 0.5 μl was injected into the prefrontal cortex.In group L + ME, 1 μmol/L endothelin + 1 μmol/L MT 1/2R antagonist + 1 μmol/L melatonin 0.5 μl was injected into the prefrontal cortex.In group P + ME, 1 μmol/L endothelin + 1 μmol/L MT 2R antagonist + 1 μmol/L melatonin 0.5 μl was injected into the prefrontal cortex.T-maze and the open field tests were performed at 1 week after administration. Results:Experiment Ⅰ There was no significant difference in the locomotor speed in open field test among C, M and ME groups ( P>0.05). The rate of correct selection in T-maze test was significantly lower in M and ME groups than in group C and higher in group ME than in group M( P<0.05). Experiment Ⅱ There was no significant difference in the locomotor speed in open field test among the four groups( P>0.05). Compared with group M, the rate of correct selection in open field test was significantly increased in ME and P+ ME groups ( P<0.05), and no significant change was found in group L+ ME ( P>0.05). Compared with group ME, the rate of correct selection in open field test was significantly decreased in group L+ ME ( P<0.05), and no significant change was found in group P+ ME( P>0.05). Conclusion:Melatonin can attenuate prefrontal cortex ischemia-induced cognitive impairment in the rats, and the mechanism is related to activation of MT 1R.
ABSTRACT
To evaluate the effect of exogenous hydrogen sulfide on phenotypic transformation of alveolar macrophages in a mouse model of endotoxin-induced acute lung injury (ALI).Methods Thirty pathogen-free healthy male C57BL/6 mice,aged 8 weeks,weighing 18-20 g,were divided into 3 groups (n =10 each) using a random number table:sham operation group (group Sham),group ALI and exogenous hydrogen sulfide group (group NaHS).In group Sham,normal saline was intratracheally instilled and intraperitoneally injected.In ALI and NaHS groups,lipopolysaccharide 20 mng/kg was intratracheally instilled,and normal saline and sodium hydrosulfide (28 μmol/kg) 100 μl were intraperitoneally injected,respectively,every day.Mice were sacrificed at day 3 after administration of lipopolysaccharide,and lungs were removed for measuremnent of the lung coefficient and expression of inducible nitric oxide synthase (iNOS) and arginase (by immunohistochemistry) and for microscopic examination of the pathological changes.Lung injury was evaluated by the index of quantitative assessment (IQA).Results Compared with group Sham,the lung coefficient and IQA were significantly increased,and the expression of iNOS and arginase in lung tissues was up-regulated in group ALI (P＜0.05).Compared with group ALI,the lung coefficient and IQA were significantly decreased,the expression of iNOS in lung tissues was down-regulated (P＜0.05),and no significant change was found in the expression of arginase in lung tissues in group NaHs (P＞0.05).Conclusion Exogenous hydrogen sulfide mitigates endotoxin-induced ALI through inhibiting phenotypic transformation of alveolar macrophages to M1 subtype in mice.