Objective: To compare the effects of electroacupuncture (EA) preconditioning and post-conditioning on hippocampal neuronal nitric oxide synthase (nNOS) expression in rats with anxiety-like behavior, so as to explore the reasonable EA intervention time.
Methods: Forty-two SD rats were randomly divided into 6 groups:normal 1, normal 2, anxiety model 1, an-xiety model 2, EA-pre-conditioning and EA-post-conditioning. The anxiety model was established by giving the rats with repeated foot shock stimulation (0.8 mA, 2-25 s/time, 10 times in 5 min) combined with isolation-raising. Before or after modeling, EA stimulation was applied to "Baihui" (GV 20) and "Yintang" (GV 29) for 20 min, once a day for 7 days. Elevated plus maze (EPM) tests were performed to determine the percentages of time spent in the open arms and the percentages of entries into the open arms in 5 min for evaluating the animals' anxiety-like behavioral activities. The reverse transcriptase polymerase chain reaction (RT-PCR) was used to detect hippocampal nNOS mRNA expression and the immunohistochemical staining adopted to detect the expression of nNOS protein in the hippocampal CA 1 and CA 3 areas, respectively.
Results: Compared with their own normal control group 1 and 2, both the percentage of time spent in the open arms and the percentage of entries into the open arms were significantly decreased in model group 1 and 2 (P<0.05, P<0.01). After pre- and post-conditioning of EA, the decreased proportions of time spent and entries into the open arms were considerably increased (P<0.05), suggesting an improvement of anxiety-like behavior activities after EA intervention. The expression levels of hippocampal nNOS mRNA and nNOS protein in the hippocampal CA 3 region were significantly higher in the model group 1 and 2 than in their own normal control group 1 and 2 (P<0.01), but those of nNOS protein in the CA 1 area were markedly lower in the model group 1 and 2 than in their own normal control group 1 and 2 (P<0.01). Following pre- and post-conditioning of EA, the increased expression levels of nNOS mRNA and protein of CA 3 area and the decreased level of nNOS protein of CA 1 area were all notably reversed (P<0.05, P<0.01).
Conclusions: Both pre- and post-conditioning of EA can improve anxiety-like behavior in anxiety rats, which may be associated with its effects in down-regulating hippocampal nNOS expression.