| Part I Clinical risk factors of depressive symptoms in patients with epilepsyObjectives:To investigate the relationships between demographic data, seizure-related factors, antiepileptic drugs (AEDs) taking and depressive symptoms in patients with epilepsy, determining the major clinical risk factors of depression.Methods:Patients with epilepsy who visited our epileptic clinic from 2010 to 2012 were included. The clinical data were collected; Hamilton Depression Rating Scale (HAMD), National Hospital Seizure Severity Scale (NHS3), and Pittsburgh Sleep Quality Index (PSQI) were evaluated. Results:A total of 116 patients with epilepsy were recruited. They were divided into three groups. Age, duration of epilepsy, percentages of patients with partial seizures, history of status epilepticus (SE), using topiramate (TPM) or clonazepam (CZP), and using greater than or equal to 2 types of AEDs were all significantly higher in patients with moderate depressive symptoms than patients without depression. HAMD scores were positively correlated with age, duration of epilepsy, and the number of AEDs taking respectively. PSQI scores were positively correlated with HAMD scores in patients with depressive symptoms. Age greater than 35 years, females, having partial seizures, history of SE and using TPM were independent predictors of depressive symptoms in patients with epilepsy by regression analysis. Conclusions:Age greater than 35 years, females, having partial seizures, history of SE, and using TPM might become risk factors of depressive symptoms in patients with epilepsy. Part II Increased ratio of glutamate/glutamine to creatine in the righthippocampus contributes to depressive symptoms in patients with epilepsyObjective:Our study aimed to investigate whether the glutamatergic system in the hippocampus is correlated with depressive symptoms in patients with epilepsy.Methods:Patients with epilepsy who met the selective criteria were recruited and evaluated by Hamilton Depression Rating Scale (HAMD), Mini Mental State Examination (MMSE), and the National Hospital Seizure Severity Scale (NHS3). The recruited patients were divided into three groups on the basis of their HAMD scores. Single voxel proton magnetic resonance spectroscopy (1H-MRS) was carried out to measure hippocampal metabolisms in all of the patients, and the values of N-acetylaspartate (NAA), choline (Cho),creatine (Cr), and glutamate and glutamine (Glx) were aquired. We compared the ratios of hippocampal NAA/Cr, Cho/Cr, and Glx/Cr among the three groups.Pearson correlation analysis and multiple linear regression analysis were performed to investigate any correlation between the variables of hippocampal metabolites and HAMD scores. Results:Fifty patients who met the criteria were recruited. The ratio of male and female was 28:22. The range of age was from 17 to 53 years, with an average age of 33.38±11.01 years. All of the patients had normal brain MRI scan.1H-MRS analysis showed that the ratio of glutamate/glutamine to creatine (Glx/Cr) in the right hippocampus was significantly increased in patients with moderate depression and correlated positively with HAMD scores. Multiple linear regression analysis showed that the ratio of Glx/Cr in the right hippocampus was an independent risk factor relating to depressive symptoms in patients with epilepsy. Conclusion:The ratio of right hippocampal Glx/Cr was positively correlated with severity of depressive symptoms in patients with epilepsy, and might become a predictor of depression in patients with epilepsy. A disturbance of the hippocampal glutamatergic system may be involved in the pathogenesis of depression in epilepsy.Part III Comparisons between the lithium chloride-pilocarpine rat chronic epilepsy model associated depressive behaviors and the chronic unpredictable mild stress depression model and studies on glutamatergic influencesObjective:Establishment of chronic rat epilepsy model induced by lithium chloride (Licl) and pilocarpine, screening depressive behaviors by behavioral tests, establishing chronic unpredictable mild stress (CUMS) depression model as the positive control, comparing the differences of behaviors and pathological changes between epilepsy associated depression and primary depression, and exploring whether glutamatergic mechanisms take part in the pathogenesis of comorbidity of epilepsy and depression. Methods:(1) Licl and pilocarpine were injected intraperitoneal (i.p.) to induce status epilepticus (SE), and diazepam was administered i.p. to terminate seizures 30min later. After a latency of 1 week, spontaneous recurrent seizures (SRS) were monitored by a video-monitoring system. The rats had been monitored for 2 weeks. At the same time, the CUMS depression model was established by different stressors daily for 21 days. All of the rats were conducted two behavioral tests including sucrose consumption test (SCT) and forced swim test (FST). SCT was conducted before SE and every week after SE, with 4 times in total. FST was carried out one time at 3 weeks after SE. The Licl-pilocarpine rat chronic epilepsy model was divided into two groups based on immobility time (IMT) of FST: epilepsy with depressive behaviors (EWD) group and epilepsy with no depressive behaviors (EWND) group. (2) Neuronal nuclei (NeuN) protein, glial fibrillary acidic protein (GFAP), glutamate (GLU), gamma-amminobutyric acid (GABA), and NR1, NR2A, and NR2B subunits of N-methyl-D-aspartate (NMDA) receptor and their phosphorylated forms in the hippocampus and cortex of rats were labeled by the indirect immunofluorescence method, and the numbers of positive cells were calculated and compared between Control, EWD, EWND, and CUMS groups. Moreover, the levels of NR1, NR2A, and NR2B subunits of N-methyl-D-aspartate (NMDA) receptor and their phosphorylated forms in the hippocampus and frontal lobe of rats were measured by western-blot analysis and compared between the four groups. (3) Ifenprodil was administered i.p. to the rats and depressive behaviors in the FST were observed and compared between Control, Control+ifenprodil, Licl-pilocarpine model, Licl-Pilo+ifenprodil groups. Results:In the Licl-pilocarpine chronic rat epilepsy model, the frequency of SRS reaching 4-5 degrees by Racine classification was ranging from 1 to 57 times in 2 weeks, with the average of 16.65± 4.11. The average latency of SRS was 11.70±3.36 d. And the average duration of SRS was 19.28±7.60 s. There were no correlations between frequency, latency, and duration of SRS and immobility time (IMT) of FST. We divided the rats of Licl-pilocarpine epilepsy model into EWD group (IMT>77.91s, n=8,34.78%) and EWND group (IMT<77.91s, n=15). There were no differences of SRS frequency, latency, and seizure duration between EWD and EWND groups. Comparisons of depressive indexes between Control, EWD, EWND, and CUMS groups indicated that IMT of EWD and CUMS groups was greater than that of Control and EWND groups, and the sucrose consumption rates (SucroRate) and sucrose consumptions per 100 grams body weight (SC/100g) after SE were also reduced more obviously in EWD and CUMS groups than Control and EWND groups. However, climbing time (CMT) of EWND group was greater than that of other three groups, and weight gain rate (WGR) of CUMS group was less than that of other three groups. The results of pathological studies showed that the number of NeuN positive cells in the hippocampus of EWD, EWND, and CUMS groups reduced significantly compared with Control group, which had no difference between EWD, EWND, and CUMS groups. The number of GFAP positive cells in the hippocampus of EWD and EWND groups increased significantly compared with Control and CUMS groups, which had no difference between EWD and EWND groups. In addition, the number of glutamate neurons in the hippocampus and cortex was greater in EWD and CUMS groups than EWND group, while the number of GABA positive cells was greater in EWD and EWND groups than Control and CUMS group, which had no difference between EWD and EWND groups. Moreover, the ratio of P-NR1 subunit of NMD A receptor positive neurons was greater in EWD and CUMS groups than EWND group, while the ratio of NR2B subunit positive neurons was greater simply in EWD group than EWND group. The results of western-blot analysis also indicated that the ratios of P-NR1/NR1, P-NR2B/NR2B in the hippocampus were greater in EWD and CUMS groups than EWND group, while the ratio of P-NR2B/NR2B in the frontal lobe was greater simply in EWD group than EWND group. After administered ifenprodil, IMT of the Licl-pilocarpine rat chronic epilepsy model was shorter significantly than other control groups. Conclusions:(1) In our study, the rate of depressive behaviors in the Licl-pilocarpine chronic rat epilepsy model was 34.78%, and no differences of SRS frequency and severity, hippocampal neuronal loss, and astrocyte proliferation were found between EWD and EWND groups. (2) The Licl-pilocarpine rat chronic epilepsy model and CUMS depression model had similar depressive behaviors of anhedonia and despair, but also had other different behavioral and physiological changes respectively. They had similar degrees of hippocampal neuronal loss, but the number of astrocytes and GABA positive cells in the hippocampus increased obviously in the Licl-pilocarpine rat chronic epilepsy model. (3) The EWD group of Licl-pilocarpine rat chronic epilepsy model and CUMS group both had greater levels of GLU neurons and higher activity of NR2B subunit of NMDA receptor in the hippocampus, and the selective antagonist of NR2B subunit (ifenprodil) alleviated depressive behaviors in the Licl-pilocarpine rat chronic epilepsy model, indicating the elevated level of GLU and activation of NR2B subunit of NMDA receptor might be involved in the pathogenesis of comorbidity of epilepsy and depression. |
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