Objective: To observe the effects of URWell on withdrawal syndrome and nitricoxide(NO)/nitric oxide synthase (NOS) system in morphine-dependent mice and its action mechanisms. Method: Sixty mice were divided into 6 groups randomly

namely the control group

model group

positive control group(clonidine

0.4 mg·kg-1·d-1

ig)

URWell group (20

10

5 g·kg-1·d-1

ig).Except the control group

the morphine-dependent mice model of other groups was established by administration of gradually increasing doses of morphine.Oral URWell or saline (control

model) was administered from the 5th day to the 10th day.The acute withdrawal was induced by naloxone (4 mg·kg-1

ip) in the 8th day

then withdrawal syndrome and body weight loss were recorded.NO concentration and NOS activity in brain tissues were tested by nitrate reductase method. Result: Compared with the model group

URWell (20

10 g·kg-1)

respectively

significantly suppressed morphine withdrawal syndrome within the 8th day and 9th day(P<0.05)

clonidine and URWell (20

10 g·kg-1·d-1) significantly reduced body weight loss in morphine-dependent mice following morphine withdrawal

as well as clonidine and URWell(20 g·kg-1)significantly inhibited levels of NO and NOS in brain tissues. Conclusion: URWell treatment attenuated withdrawal syndrome in morphine-dependent mice

and the mechanism may be associated with inhibiting NO and NOS in the brain.