BACKGROUND: Following morphine withdrawal, anxiety is associated with abnormal norepinephrine content change. However, increasing blood lactic acid content can induce anxiety or panic in patients with anxiety disorder or endogenous opioid peptide functional disorder. OBJECTIVE: This study was designed to observe the effects of electro-acupuncture, at the "Sanyinjiao" point (SP 6), on brain tissue norepinephrine and blood lactic acid content in anxiety-model mice after morphine withdrawal.DESIGN: A randomized controlled animal experiment. SETTING: This study was performed in the Laboratory of Acupuncture, Electro-acupuncture & Tuina College, Chengdu University of Traditional Chinese Medicine, from June to September 2001.MATERIALS: A total of 50 healthy Kunming male mice were provided by the Laboratory Animal Center of Chengdu University of Traditional Chinese Medicine. The protocol was performed in accordance with ethical guidelines stated in the Guide for the use and care of laboratory animals, approved by the Committee on the Care and Use of Laboratory Animals of the Institute of Laboratory Animal Resources Commission on Life Sciences, National Research Council, China (1985). Experimental reagents and equipment used were as follows: morphine hydrochloride (Lot No. 930503, Shenyang No.1 Pharmaceutical Factory, China), norepinephrine (Sigma Chemical Company, USA), fluorospectrophotometer (RF-510, Shimadzu Corporation, Japan), Han electro-acupuncture apparatus (WQ 1002, No. zun (91)-227270-588, Beijing Anlong Photoelectricity-Technique Company, China), and T-maze (self-made). METHODS: A total of 50 mice were randomly divided into 5 groups, with 10 mice in each group: blank control, T-maze, model, model + electro-acupuncture, and electro-acupuncture groups. Establishment of anxiety model after morphine withdrawal: the mouse hot plate assay was used to detect the activity of morphine. The median effective dose of morphine, 2.95 mg/kg, was defined as the base. Mice were subcutaneously administered morphine, 3 times a day, for 4 days successively (initially 2.95 mg/kg, then increased day by day, as described below). Interventions: In the model + electro-acupuncture group, after model induction, mice were subjected electro-acupuncture at bilateral "Sanyinjiao" (SP6) points using a Han electro-acupuncture apparatus with sparse-dense waves and frequency of 2-100 Hz, once a day, for 6 days. In the model group, after anxiety-model induction, mice were subjected to fixation as same as model + electro-acupuncture group within 6 days of model induction. In the electro-acupuncture group, the anxiety model was not induced and mice were subjected to fixation, electro-acupuncture and the T-maze test. In the T-maze group, the anxiety model was not induced and mice were subjected to fixation. The T-maze test was performed in the 4 groups after experiment. In the blank control group, the anxiety model was not induced and mice were subjected to fixation only.MAIN OUTCOME MEASURES: Brain tissue norepinephrine content of morphine-withdrawal anxiety mice was detected by fluorospectrophotometry after 6 days of electro-acupuncture. Blood lactic acid content was detected by visible spectrophotometry.RESULTS: A total of 50 mice were included in the final analysis. Brain norepinephrine content was significantly greater in the model group compared to the T-maze, blank control, electro-acupuncture and model + electro-acupuncture groups, (P 0.05). There was no significant difference in blood lactic acid content among the groups (P > 0.05). CONCLUSION: Electro-acupuncture lowers brain norepinephrine content but does not influence peripheral blood lactic acid content in morphine-withdrawn, anxiety-modeled mice. These results demonstrate that anxiety-inhibiting effects of electro-acupuncture, after morphine withdrawal, might be related to regulation of norepinephrine release.