Study On The Mechanism Of Neonatal Hypoglycemia-Induced Impairment Of Prepubertal Learning And Memory

Objective:Hypoglycemia is one of the most common metabolic problems in the neonatal intensive care center(NICU),especially in high-risk infants.Sustained and recurrent hypoglycemia can lead to permanent neurological impairment in newborns,including cognitive memory impairment,audiovisual impairment,cerebral palsy,and epilepsy.Animal studies have found that neonatal hypoglycemia can lead to neuronal damage in the hippocampus and cortex of rats,and this damage can last until puberty.However,the specific mechanism of neonatal hypoglycemia causing brain damage and long-term learning and memory impairment is still unclear.Therefore,in this study,by establishing a hypoglycemia model in neonatal rats,we initially explored its mechanism of impaired prepubertal learning and memory.Methods:Select 10-day-old Sprague-Dawley(SD)rats,regardless of sex,and randomly divide them into control group(Control,Ctrl)and hypoglycemia group(Hypoglycemia,HG).Neonatal rat hypoglycemia model was established by subcutaneous injection of insulin(15 U/kg)for 3 consecutive days(hypoglycemia was maintained for 4 h/d),and the Ctrl group was injected with the same volume of normal saline.After modeling:Experiment 1: Samples were collected 24 hours after the end of modeling,and stained with hematoxylin-eosin(HE)and Fluoro-Jade C(FJC)to observe the body weight between the two groups and the frontal cortex of rats after hypoglycemia Pathological changes such as necrosis and apoptosis of neurons in the cortex(Prefrontal cortex,PFC),hippocampal dentate gyrus(Dentate gyrus,DG)and other brain regions;Experiment 2: Passing the Morris water maze test(Morris water maze),MWM)to detect the learning and memory ability of rats.The brain tissue was fixed 1.5 h after the end of the MWM experiment and then immunofluorescence staining was performed for neuron activity marker(c-Fos)to explore the changes in neuron activity in the PFC and hippocampus DG area,and Golgi Staining method was used to observe the changes of neuronal dendritic spines in PFC and DG.Results:1.There was no significant difference in the mean blood glucose values between the Ctrl group and the HG group before modeling.After the subcutaneous injection of insulin,the blood sugar in the HG group dropped rapidly,and showed poor response,frequent tremors,and convulsions.The blood glucose values of the two groups were significantly different at 1,2,3,and 4 h after insulin injection.At 24 h after modeling,there was no significant difference in body weight between the two groups.2.24 hours after modeling,the shape and size of the neurons in the PFC and DG areas of the Ctrl group were consistent,the cytoplasm was evenly stained,and the nuclei were clearly visible;Cell edema,vacuoles and other manifestations,cells arranged disorderly,sparsely distributed,and the gap between neurons increased;compared with the mice in the Ctrl group,the number of FJC-positive cells in the PFC and DG of the HG group increased significantly,There is a statistical difference between the two.3.In the MWM experiment,compared with the Ctrl group,there was no statistical difference in the escape latency(the time to reach the platform)of the rats in the HG group during the training process of the visible platform period on day 1 and the hidden platform period from day 2 to day 5,On day 6(no platform period),the number of crossing the platform location was significantly reduced.4.Compared with the rats in the Ctrl group,the number of c-Fos protein-positive cells in the PFC and DG of the rats in the HG group decreased significantly after the MWM experiment.5.After the MWM experiment,the dendritic spines of the PFC and DG areas of the Ctrl group were tightly arranged and regular in shape;the dendritic spines of the PFC and DG areas of the HG group were loosely distributed,irregular in shape,and swollen and incomplete.Dendritic spine densities in the PFC and DG were significantly lower in the HG group compared with the Ctrl group.Conclusions:In summary,this study established an animal model of repeated and severe hypoglycemia in the neonatal period,which can lead to impaired learning and memory before puberty in SD rats,which may be due to the neuronal tree in the PFC and hippocampal DG area after hypoglycemia.The reduction in the number of spines leads to impaired transmission of electrical signals between neurons,which ultimately results in a decrease in neuronal activity.These findings can provide a theoretical basis for the prevention and treatment of clinical neonatal hypoglycemia and its neurological sequelae.