<p style="text-align: center;">Li Shaoyuan, Guo Xiao, Zhang Jinling, Li Liang, Rong Peijing*</p><p style="text-align: center;">(Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing 100700, China)</p><p style="text-align: justify;"><strong>Abstract</strong>：<strong>Objective</strong>: Depression is a common and multiple recrudescent psychiatric disorder. Our previous studies indicated that electric acupuncture at auricular could significantly decrease the high level score of 17 Hamilton Depression Scale. In this study, chronic unpredictable mild stimulation for 21 days was applied to make&nbsp; depression&nbsp; model.&nbsp; We’d&nbsp; like&nbsp; to&nbsp; explore&nbsp; the&nbsp; mechanism&nbsp; of&nbsp; auricular&nbsp; electric&nbsp; acupuncture&nbsp; on&nbsp; the expression of brain derived neural factor, cell proliferation and apoptosis in hippocampus. Method: 30 SD rats were divided into control (n=10), model (n=10) and auricular electric acupuncture (n=10) group. Except control group, rats in other groups should be under the CUMS for consecutive 21 days to make depression model, including fasting food and water, ice water swimming, tail clip, day and night inversion, wet packing and hot plate. The electric acupuncture is on the auricular conchea with 20 Hz and 2 mA 30 min per day for 28&nbsp; days.&nbsp; Hippocampus&nbsp; of&nbsp; all&nbsp; animals&nbsp; were&nbsp; collected&nbsp; by&nbsp; the&nbsp; end&nbsp; of&nbsp; the&nbsp; experiments.&nbsp; Western&nbsp; blot&nbsp; and immunohistochemistry were used to explore the expression of BDNF and cell proliferation and apoptosis in hippocampus respectively. <strong>Results</strong>: Compared with control group, the expression of BDNF in hippocampus of model rats decrease significantly (P&lt;0.01) and electric acupuncture can inverse it obviously (P&lt;0.01); the number&nbsp; of&nbsp; proliferation&nbsp; cell&nbsp; is&nbsp; more&nbsp; than&nbsp; that&nbsp; in&nbsp; control&nbsp; group&nbsp; (P&lt;0.01)&nbsp; and&nbsp; there&nbsp; was&nbsp; no&nbsp; significant difference between electric acupuncture group and control group(P&gt;0.05). The positive cells of apoptosis in hippocampus are less than control group but electric acupuncture can inhibit the decline of the apoptosis cell(P&lt;0.01).&nbsp; <strong>Conclusion</strong>:&nbsp; Auricular&nbsp; electric acupuncture&nbsp; can up-regulate&nbsp; the&nbsp; expression&nbsp; of BDNF and improve the condition of cell proliferation and apoptosis in hippocampus.</p><p><strong>Key words</strong>: depression, auricular electric acupuncture, hippocampus, proliferation, apoptosis</p><p><br/></p>