Objective: To observe the effect of electroacupuncture (EA) of "Zusanli"(ST 36) on nitric oxide synthase (NOS) mRNA expression in the brain in rats with morphine abstinence syndrome for studying the biomolecular mechanism of acupuncture in improving abstinence syndrome. Methods: Rat abstinence syndrome model was established by continuous muscular injection of morphine to the hindlimbs for 15 days. A total of 24 rats were randomly and evenly assigned to abstinence syndrome (AS) group

EA (ST 36) group and L nitroarginine (NAME) group. Expression of nNOS mRNA in the brain tissues was determined by using the reverse transcription polymerase chain reaction (RT PCR) method. EA (2/100 Hz

10 V

duration of 30 min/time

once daily and 7 days altogether) was delivered to bilateral ST 36 via two inserted needles. Results: Comparison of abstinence symptoms among the three groups showed that the scores of EA and L NAME groups were significantly lower than those of AS group at 24 hr

48 hr and 72 hr after withdrawal of morphine injection ( P <0.01). In comparison with AS group

nNOS mRNA expression of EA group and L NAME group was lower clearly

suggesting a suppression of nNOS mRNA expression by EA. Conclusion: In morphine natural abstinence syndrome rats

acupuncture of ST 36 may down regulate nNOS mRNA expression in brain tissues.