| ObjectiveTo explore the effect and partial mechanism of bergamot essential oil aerosol inhalation on hippocampal neuroplasticity of depression model rats,and to provide scientific basis for clinical trialsMethodsFirstly,BEO was extracted by steam distillation,and its main components were identified by Gas chromatography-mass Spectrometry(GC-MS).SD rats were randomly divided into Control group,Model group,fluoxetine group(10mg/kg)and BEO group(2.5%W/w),with 15 rats in each group.After 5 weeks of chronic unpredictable mild stress(CUMS)modeling and drug intervention,the effects of BEO on depression model rats were evaluated by sugar water preference test,forced swimming test,open field test and body weight.Secondly,the hippocampal tissues of each group were extracted and fixed,and the number of Nisi was detected by Nisi staining.The changes of cell body number and dendrite spinous density of neurons were detected by Golgi staining.Immunohistochemical and Western-blot methods were used to detect the changes of synaptophysin(SYP)and Postsynaptic Density Protein-95(PSD-95),key proteins of hippocampal neuroplasticity in rats.Finally,ELISA was used to investigate the levels of 5-hydroxytryptamine(5-HT),insulin-like growth factor-1(IGF-1),brain-derived neurotrophic factor(BDNF),tumor necrosis factor-α(TNF-α)and interleukin-1β(IL-1β).Results1.BEO was successfully extracted by steam distillation,and its main components were identified by GC-MS as 61.69% L-limonene,28.02% γ-terpinene,3.52% α-pinene,2.8% β-pinene,1.28% α-phellandrene,consistent with the results of previous studies.2.Sugar water preference experiment: compared with the Control group,the 12 h sugar water preference rate of the Model group rats decreased,and the difference was statistically significant(P<0.05);compared with the Model group,the 12 h sugar water preference rate of the BEO group rats increased significantly,the difference was statistically significant(P<0.05).There was no significant change between the BEO group and the Flu group(P>0.05).Forced swimming test: compared with the Control group,the immobility time of the rats in the Model group increased and the struggling time decreased,and the difference was statistically significant(P<0.05).The time of struggle increased,and the difference was statistically significant(P<0.05).There was no significant change between the BEO group and the Flu group,and there was no statistical difference(P>0.05).Open field test: compared with the Control group,the total movement distance,peripheral movement distance and activity time of the Model group were decreased,and the rest time was increased,and the difference was statistically significant(P<0.05).The total movement distance,peripheral movement distance and activity time of the rats increased significantly,while the rest time of the rats decreased,and the difference was statistically significant(P<0.05).Compared with the Flu group,the total movement distance and activity time of the rats in the BEO group did not change significantly,there was no statistical difference(P>0.05),the peripheral movement distance of the rats in the BEO group was decreased,and the difference was statistically significant(P<0.05),and the rest time of the rats in the BEO group was increased,and the difference was statistically significant(P<0.05).Body weight: compared with the Control group,the weight of the rats in the Model group decreased,and the difference was statistically significant(P<0.05);compared with the Model group,the weight of the rats in the BEO group increased,and the difference was statistically significant(P<0.05);compared with the Flu group,the weight of the rats in the BEO group increased,and the difference was statistically significant(P<0.05).3.Nissl staining: compared with the Control group,the number of Nissl bodies in the hippocampus of the rats in the Model group was significantly decreased,and the difference was statistically significant(P<0.05);compared with the Model group,the number of Nissl bodies in the hippocampus of the rats in the BEO group increased,and the difference was statistically significant(P<0.05);compared with the Flu group,the BEO group had no significant change,and there was no statistical difference(P>0.05).Golgi staining: compared with the Control group,the dendritic length of neuron and the density of dendritic spines in the hippocampal DG area of the rats in the Model group decreased,and the difference was statistically significant(P<0.05);compared with the Model group,the dendritic length of neuron and the density of dendritic spines in the hippocampal DG area of the rats in the BEO group increased,and the difference was statistically significant(P<0.05);compared with the Flu group,the dendritic length of BEO neuron was reduced,and the difference was statistically significant(P<0.05);compared with the density of dendritic spines in the Flu group,there was no significant difference between the two groups(P>0.05).4.Immunohistochemistry and Western-Blot experiments: compared with the control group,the expression of key proteins PSD-95 and SYP in the hippocampus of the rats in the Model group was decreased,and the difference was statistically significant(P<0.05);compared with the Model group,the expressions of key proteins PSD-95 and SYP in hippocampal neuroplasticity of the rats in the BEO group were increased,and the difference was statistically significant(P<0.05).Immunohistochemical experiments showed that compared with the Flu group,the expression of PSD-95 in the CA1 region of the BEO group was increased,and the difference was statistically significant(P<0.05);the PSD-95 in CA2,CA3 and DG regions in BEO group had a tendency to increase,but there was no statistical difference(P>0.05);compared with the Flu group,the expression of SYP protein in the CA3 and DG regions of the BEO group was decreased,and the difference was statistically significant(P<0.05);there was no significant change in the expression of SYP protein in CA1 and CA2 regions in BEO group,and there was no statistical difference(P>0.05).WesternBlot experiment found that there was no significant change between the BEO group and the Flu group,and there was no statistical difference(P>0.05).5.Elisa experiment: compared with the control group,the serum and cerebrospinal fluid5-HT levels of the rats in the Model group were decreased,and the difference was statistically significant(P<0.05);compared with the Model group,the serum 5-HT level in the BEO group was significantly increased,and the difference was statistically significant(P<0.05);compared with the Flu group,the serum 5-HT level in the BEO group was decreased,and the difference was statistically significant(P<0.05).Compared with the Control group,the expressions of IGF-1 in serum and cerebrospinal fluid of the Model group were significantly decreased,and the difference was statistically significant(P<0.05),the expression of IGF-1 in the hippocampus of the Model group tended to decrease,but there was no statistical difference(P>0.05);compared with the Model group,BEO could increase the levels of IGF-1in serum and cerebrospinal fluid of rats,and the difference was statistically significant(P<0.05),BEO also tended to increase the level of IGF-1 in the hippocampus of rats,but there was no statistical difference(P>0.05);compared with the Flu group,the expression of IGF-1in serum and cerebrospinal fluid of the BEO group was increased,and the difference was statistically significant(P<0.05).Compared with the Control group,the serum,cerebrospinal fluid and hippocampal BDNF of the Model group had a decreasing trend,but there was no statistical difference(P>0.05);compared with the Model group,the serum,cerebrospinal fluid and hippocampal BDNF of the BEO group had no significant changes,and there was no statistical difference(P>0.05);compared with the Flu group,the serum,cerebrospinal fluid and hippocampal BDNF of the BEO group had no significant changes,and there was no statistical difference(P>0.05).Compared with the Control group,the expression of serum IL-1β in the Model group was significantly increased,and the difference was statistically significant(P<0.05);compared with the Model group,the levels of serum IL-1β in the BEO and Flu groups were significantly decreased,and the difference was statistically significant(P<0.05);compared with the Flu group,the serum IL-1β level in the BEO group was significantly lower,and the difference was statistically significant(P<0.05).Compared with the control group,the expression levels of TNF-α in serum,cerebrospinal fluid and hippocampus of the rats in the Model group did not change,and there was no statistical difference(P>0.05);compared with the Model group,the levels of TNF-α in the serum,hippocampus and cerebrospinal fluid of the BEO and Flu groups did not change significantly,and there was no statistical difference(P>0.05).Conclusion1.Aerosol inhalation of BEO can alleviate depression-like behavior in CUMS depression model rats.2.BEO can improve the neuroplasticity of hippocampus in rats with depression.3.The antidepressant mechanism of BEO may be related to the increase of serum 5-HT content,serum and cerebrospinal fluid IGF-1 content,and decrease of serum IL-1β content in depression model rats. |
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