Effect of repetitive transcranial magnetic stimulation on the improvement of behaviors and neuronal apoptosis in rats with chronic stress induced depression

Objective To explore the effects of repetitive transcranial magnetic stimulation on behaviors and hippocampus neuronal apoptosis in rats with chronic stress-induced depression. Methods 40 male SD rats of SPF grade were randomly divided into normol control group(n=8) and model preparation group(n=30) after screening.Rats in model preparation group were singly housed and given chronic unpredictable mild stress(CUMS) to build depression model.Excluding unsuccessful modeling rats, the model preparation group was divided into three groups: model group(n=8, without any treatment), rTMS group(n=8, with the intervention of 10 Hz rTMS) and shame group(n=8, simulation of rTMS environment without rTMS stimulus). The changes of behaviors in each group were detected by weight measurement, sucrose consumption test and open-field test.The changes of morphology of hippocampal neurons were detected by Nissl's staining.The changes of Bax in hippocampal neuron were detected by Immunohistochemical staining. Results (1)Behavioral results showed stress for 21 d could make rat behavior scores decrease significantly(all P<0.05), and rTMS intervention could significantly improve their behavior scores (all P<0.01). Compared with model group, the weight reduction rate(0.32±0.05)%, the score of sucrose consumption test(7.03±1.02) and the score of open field test(8212.41±1416.15, 8.75±1.58) in rTMS group was higher(P<0.01). (2)Nissl staining showed stress for 21 d could make the number of hippocampal CA3 neurons was reduced, cell morphology was poor, and the number of Nissl bodies was reduced.rTMS intervention could increase the number of hippocampal CA3 neurons, cell morphology was integral and the number of Nissl bodies was increased.(3) Immunohistochemistry results showed stress for 21 d could cause the number of Bax cell were significantly increased(P<0.01), and rTMS intervention can make the number of Bax cell were significantly lower(P<0.01). Conclusion rTMS intervention improves the depressive behavior in chronic stress depression model rats and inhibits the apoptosis, which might work through inhibition of neuron apoptosis and decline of Bax expression in hippoeampal neurons. Key words: Depression; Repetitive transcranial magnetic stimulation; Hippocampus; Bax