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.

Objective Analyze the surveillance results of foodborne illness from a level A tertiary general hospital in Shandong Province from 2019 to 2021,to provide a realistic basis for the continuous development and improvement of foodborne disease surveillance.Methods The data were collected from a level A tertiary general hospital in Shandong Province from 2019 to 2021 in the food safety risk assessment business application platform of national health insurance information project of National Health Security Disease Control Information System,and stool/anal swab samples were collected as required for pathogen detec-tion.Results From 2019 to 2021,a total of 2 323 cases of foodborne diseases were reported and 682 samples were collected,with a sampling rate of 29.36％,and 134 positive cases were detected,with a detection rate of 19.65％.The difference between the detection rates of different years was statistically significant(P＜0.05).The detection rate of norovirus was the highest(9.53％),followed by Vibrio parahaemolyticus(8.94％)and Salmonella(1.91％).The difference between the detection rates of different pathogens was statistically significant(P＜0.05).The sex ratio of 2 323 cases was 1:1.28.Among the different age distributions,20-29 years old accounted for the highest proportion(29.19％),followed by 30-39 years old(27.21％)and＜20 years old(11.71％).The highest number of cases was reported from June to September,the peak was reached from July to Au-gust,and the number of cases was gradually reduced in October and later.Among different occupational groups,housework and unemployed people accounted for the highest proportion(30.18％),followed by farmers(15.93％),students(13.65％)and commercial service workers(11.80％).The main symptoms of the digestive system were diarrhea in 2 093 cases(90.10％),abdominal pain in 1 741 cases(74.95％),nausea in 1 575 cases(67.8％)and vomiting in 1 401 cases(60.31％).The main diarrhea was watery stool in 1 954 cases(84.12％).The main systemic symptoms were fatigue in 454 cases(19.54％)and dehydration in 212 cases(9.13％).The main clinical diagnosis was acute gastroenteritis in 1 980 cases(85.23％)and infec-tious diarrhea in 199 cases(8.57％).The suspected exposed foods were mainly aquatic animals and their products(25.10％)and meat and meat products(19.37％).The main eating places of suspected exposed foods were families(57.34％),followed by restaurants(21.91％),other places(5.94％)and street food stalls(5.21％).Conclusion From 2019 to 2021,the pathogens of foodborne diseases detected were mainly norovirus and Vibrio parahaemolyticus,mainly in the age group of 20 to 39 years old,and the occupation distribution was mainly household and unemployed people,farmers,students and commercial serv-ice personnel,with digestive system symptoms such as nausea,vomiting,abdominal pain and diarrhea.The suspected exposed foods are mainly aquatic animals and their products and meat and meat products,and the main eating places are families,restau-rants and street food stalls.The surveillance and reporting of foodborne diseases should continue to be strengthened in the future.