abstract
Purpose: Comorbid depression is common in patients with epilepsy. However, the epilepsy-associated depression is always atypical and has not been fully recognized by neurologists. This study aimed to compare the behavioral and pathological changes between the chronic lithium chloride-pilocarpine rat epilepsy model (Licl-pilocarpine model) and Chronic Unpredictable Mild Stress rat depression model (CUMS model), trying to find some differences between epilepsy-associated depression and primary depression. Methods: The Licl-pilocarpine model and CUMS model were established respectively and simultaneously. Spontaneous seizures were recorded by video monitoring. Forced swim test (FST) and sucrose consumption test (SCT) were performed to test depressive behaviors. Immobility time (IMT) and climbing time (CMT) in FST, sucrose preference rate (SPR) in SCT, and weight gain rate (WGR) were adopted to represent severity of depressive behaviors in rats. Immunofluorescent staining was conducted to measure expressions of neuronal specific nuclear protein (NeuN), glial fibrillary acidic protein (GFAP), and CD11b in the hippocampus of Licl- Q6 28 pilocarpine model, CUMS model, and Control group. Results: Significantly, more prolonged IMT was observed in both Licl-pilocarpine model (p b 0.05) and CUMS model (p b 0.01) than Control group. But decreased WGR was only seen in CUMS model. The percentage of rats with CMT greater than 100 s was significantly higher in Licl-pilocarpine model than CUMS model (p b 0.05). Increased CMT was observed in Licl-pilocarpine model with mild depression subgroup (EMD,IMT ≤ 100 s) even compared with Control group. Neuronal loss was both found in Licl-pilocarpine model and CUMS model when comparing with Con- trol group (p b 0.05). However,the number of GFAP and CD11b staining cells was both greater in Licl-pilocarpine model than CUMS model and Control group (p b 0.05). Conclusion: There were some different depressive behavioral and hippocampal pathological changes between Licl- pilocarpine and CUMS models except for some common features. Gliosis and microglial activation might be more involved in the pathophysiology of epilepsy-associated depression than primary depression.