Effects Of Long-term Use Of Propofol On Midbrain Dopaminergic Neurons In Mice

Propofol is a widely used ultra-short-acting intravenous anesthetic that produces sedative,hypnotic,and amnestic effects.Due to its fast onset,rapid action,short half-life and easy control,it is very popular among anesthesiologists in various countries.Because propofol has a strong euphoric effect when used in subanesthetic doses,it produces a subjective sensation of psychostimulants like cocaine and is now the fourth most abused drug.The use of propofol to relieve pain,stress,anxiety,insomnia is the main cause of propofol abuse and dependence.After long-term injection of propofol,patients may experience bradykinesia,abnormal posture gait,muscle twitching or tremors,and emotional abnormalities such as depression,anxiety,and depression.Midbrain dopaminergic neurons play an important role in regulating body movement,reward,mood,and drug addiction,but whether these clinical symptoms are related to the damage of midbrain dopaminergic neurons is still unclear.This study intends to observe the effect of long-term use of propofol on motor function and mood-related behavior by constructing a mouse model of intermittent intraperitoneal injection of propofol once a month,whether propofol can affect midbrain dopaminergic Neurons produce cues for toxic effects.Objectives:To study the neurotoxic effects of long-term injection of propofol on midbrain dopaminergic neurons in mice preliminarily.Methods:1.The percentage of disappearance of righting reflex was used to determine the dose of 1% propofol required for anesthesia in mice.The mice were intraperitoneally injected with 25 mg/kg,50 mg/kg and 75 mg/kg propofol respectively,and the loss of righting reflex was observed and the percentage recorded.2.The mice were randomly divided into a propofol injection group(group P)and a saline control group(group C).Group P mice were intraperitoneally injected with 75mg/kg propofol once a day,for 30 consecutive days,mice in group C were given the same amount of normal saline,and others are the same as P group.3.After 30 days of continuous injection,1 day(T1)and 30 days of withdrawal(T2),the motor function and emotion related behavior of the mice in the P and C groups were tested by using the rotation test and open field experiment the mine experiment.4.Tyrosine hydroxylase antibody(Th)was used for Immunofluorescence staining to count the number of SNc and VTA dopamine neurons in the midbrain of each group.At the same time,the expression of Th in SNc,VTA dopamine neurons and thestriatum dopaminergic nerve fiber terminals were observed at T1 andT2.5.Dopamine transporter antibody(DAT)was used to observe the expression of dopaminergic nerve fiber terminal in striatum of the mice at T1 and T2.Results:1.The effects of long-term injection of propofol on behavior in mice(1)Mice were injected intraperitoneally at 25 mg/kg,50 mg/kg,and 75 mg/kg at a concentration of 1% propofol.The percentage of righting reflex disappeared was13.3%,46.7%,and 100%,respectively.According to the literature report,it was initially determined that the injection dose of propofol was 75 mg/kg.(2)After long-term injection of propofol,the mice were significantly shorter than the control group at the riding time,mobile time and travel distance at T1.Stop the drug for 30 days,the propofol group mice were still significantly shorter than the control group mice(P <0.01).(3)After long-term injection of propofol,the mice were significantly shorter than the control group at the line crossing,rearing times,searching times and defecating time at T1.Stop the drug for 30 days,the propofol group mice were still significantly less than the control group mice(P <0.01).2.The effect of long-term injection of propofol on SNc and VTA dopaminergic neurons in the midbrain of mice.(1)The effect of long-term injection of propofol on SNc dopaminergic neurons in the midbrain of mice.After long-term injection of propofol,the expression of Th in the SNc dopaminergic neurons in the midbrain of mice was significantly decreased at T1,and it did not improve after 30 days of stopping the drug,which was still significantly lower than that of the control mice(P <0.01).In addition,there was no significant difference in the number of dopaminergic neurons in the midbrain SNc Th+ between the two groups(P> 0.05).There was no change in the morphology of the dorsal striatum in the two groups at T1 and T2,but the fluorescence intensity of the Th-positive region in the striatum of the P group was significantly weaker than that of the C group at T1 and T2(P <0.01).(2)The effect of long-term injection of propofol on VTA dopaminergic neurons in the midbrain of mice.After long-term injection of propofol,the expression of Th in the VTA dopaminergic neurons in the midbrain of mice was significantly decreased at T1,and it did not improve after 30 days of stopping the drug,which was still significantly lower than that of the control mice(P <0.01).In addition,there was no significant difference in the number of dopaminergic neurons in the midbrain VTA Th+ between the two groups(P> 0.05).There was no change in the morphology of the dorsal striatum in the two groups at T1 and T2,but the fluorescence intensity of the Th-positive region in the striatum of the P group was significantly weaker than that of the C group at T1 and T2(P <0.01).Conclusions:1.Long-term injection of propofol may cause motor dysfunction and abnormal emotional behavior in mice.2.Motor dysfunction in mice after long-term injection of propofol may be related to the decrease of Th expression in dopaminergic neurons and dorsal striatum dopaminergic nerve fibers in the midbrain of mice,but not the number of neurons.3.The abnormality of emotion-related behavior caused by long-term injection of propofol may be related to the decrease of Th and DAT expression in the VTA dopaminergic neurons and ventral striatum dopaminergic nerve fibers,but not related to the number of neurons.