Electroacupuncture restores hippocampal synaptic plasticity via modulation of 5-HT receptors in a rat model of depression

OBJECTIVE: The study aimed to determine the effect of electroacupuncture (EA) on Wistar Kyoto (WKY) depressive model rats and explore the possible mechanism of EA on hippocampal CA1 region neuronal synaptic plasticity. METHODS: The male WKY rats were randomized to three experimental groups (EA, Sham EA, and Model group, n = 8/group), and Wistar rats as the normal control group (n = 8). EA treatment was administered once daily for 3 weeks at acupuncture points Baihui (GV20) and Yintang (EX-HN3). In the Sham EA group, acupuncture needles were inserted superficially into the acupoints without electrical stimulation. On day 21, the forced swimming test (FST), open field test (OFT) and sucrose preference test (SPT) were conducted. After the behavioral tests, long-term potentiation (LTP) was evoked at Schaffer collateral-CA1 synapses in hippocampal slices in vitro by electrophysiological recording, 5-HTT, 5-HT1A and 5-HT1 B protein levels in the hippocampus CA1 region were examined by using Western blot. RESULT: EA significantly decreased immobility in FST and improved sucrose intake compared with the Sham EA and Model groups. The center time and total move time in OFT were significantly increased in the EA group compared to the Model group. Compared with those of the Sham EA and Model groups, the fEPSP slope of the EA group increased significantly, and the LTP induction was successful. EA significantly decreased 5-HTT protein expression in the hippocampus CA1 region in comparison to the Sham EA and Model groups. Additionally, EA down regulated the 5-HT1A protein expression in the hippocampus CA1 region in comparison to the Sham EA group. CONCLUSION: EA could ameliorate depressive-like behaviors by restoring hippocampus CA1 synaptic plasticity, which might be mainly mediated by regulating 5-HT receptor levels.