ABSTRACT
Objective To investigate the cell morphology and expression of 5-hydroxytryptamine transporter(5-HTT) in hippocampal CA1 region of depression rats induced by adolescent and post-adult stress,and to observe the inter-vention effect of modified Sini San (MSS). Methods One hundred and thirty-two Wistar rats were randomly divided into blank group,model group,JSS group,and fluoxetine group,33 rats in each group. And then the rats in each group were randomly subdivided into adolescent group, adult group, post-adult group acaccording to the age day, 11 rats in each subgroup. Age day 44,56 and 78 were used as the sampling time points for adolescent group,adult group,post-adult group respectively. Chronic unpredictable mild stress(CUMS)rat model was used. From day 21 to 44 and from day 57 to 78, the rats were modeled and given medication, but from day 44 to 55, the rats were fed normally. The rat general condition and body mass of various groups were observed,the cell morphology of hippocampal CA1 region was observed by hematoxylin-eosin (HE) staining , and the distribution of 5-hydroxytryptamine transporter (5-HTT)positive cells in CA1 region of hippocampus was observed by immunohistochemical staining. Results The general condition of the rats at different age stages in the model group was poor,while that in MSS group and fluoxetine group was improved obviously. The body mass of rats at different age stages in the model group was obviously decreased (P<0.01 compared with the blank group). After adulthood stage,the body mass of rats in model group, MSS group, and fluoxetine group was lower than that of the blank group(P < 0.01), but there was no difference between the 3 groups (P > 0.05). In aspect of cell morphological manifestation in hippocampal CA1 region, rats in the adolescent model group had more deeply-staining atrophy neurons, with unclear hyperchromatic nucleus and cytoplasm. The morphological manifestations in modeled rats at adult stage and post-adulthood stage showed progressive aggravation,manifested as a large amount of neurons stained deeply with unclear nucleus and cytoplasm, and a small amount of glial cells proliferated. Compared with the model group at the same stage,the neuronal atrophy and deeply staining decreased in fluoxetine group and MSS group. The average optical density value of 5-HTT expression in the model group was decreased significantly at the adult stage and after adulthood stage(P<0.05 or P<0.01 compared with the blank group). Compared with the model group, the average optical density value of 5-HTT expression in MSS group after adulthood stage, and in the fluoxetine group at the adult stage and after adulthood stage were increased (P<0.05 or P<0.01). Conclusion Rats suffering CUMS in adolescence presents depressive behavior, and post-adult stimulation can aggravates depression. 5-HTT expression in hippocampus may be an important pathway for MSS to achieve the therapeutic efficacy.