OBJECTIVE：To stu dy the mechanism of improvement effects of Gastrodin injection on methamphetamine induced neurotoxic damage in rats via nNOS pathway. METHODS ：SD rats were randomly divided into control group ，methamphetamine group，regular-dose of gastrodin group ，double-dose of gastrodin group ，negative control （NC）adenovirus group ，NC adenovirus+ methamphetamine group ，NC adenovirus+gastrodin group and nNOS adenovirus+gastrodin group ，with 10 rats in each group. Control group was given normal saline intraperitoneally ，twice a day. Methamphetamine group was given methamphetamine intraperitoneally（7.5 mg/kg），twice a day. Regular-dose and double-dose of gastrodin groups were respectively given different doses of Gastrodin injection （10，20 mg/kg）intraperitoneally 30 min earlier ，once a day ，and then given methamphetamine intraperitoneally by the same way as methamphetamine group. NC adenovirus group was given NC adenovirus （4.8×107 PFU）3 μL once in the striatum and normal saline intraperitoneally ，twice a day. NC adenovirus+methamphetamine group was given NC adenovirus by the same way and methamphetamine （7.5 mg/kg）intraperitoneally，twice a day. NC adenovirus+gastrodin group was given NC adenovirus+methamphetamine by the same way ，meanwhile given Gastrodin injection intraperitoneally （20 mg/kg）30 min before methamphetamine ，once a day. nNOS adenovirus+gastrodin group was given nNOS adenovirus and methamphetamine by the same way ，meanwhile given Gastrodin injection intraperitoneally （20 mg/kg）30 min before methamphetamine ，once a day. Each group was given relevant medicine intraperitoneally 1 mL/100 g，for consecutive 3 days. The stereotyped behavior of rats were observed and scored ；the apoptotic rate ，the protein expression of apoptotic factors （Bcl-2，Bax，Cleaved caspase- 3），the levels of oxidative stress factors （MDA，SOD，GPx） and NO ，the protein expression of nNOS were detected. RESULTS ： Compared with control group ，stereotyped behavior score ，cell apoptosis rate of striatum ，protein expression of Bax ，Cleaved caspase-3 and nNOS ，the levels of MDA and NO were increased significantly in methamphetamine group ；while the protein expression of Bcl- 2 and the levels of SOD and GPx were decreased significantly （P＜0.05 or P＜0.01）. Compared with methamphetamine group ，stereotyped behavior score ，cell apoptosis rate of striatum ，protein expression of Bax ，Cleaved caspase- 3 and nNOS ，the levels of MDA and NO were decreased significantly in regular-dose and double-dose of gastrodin groups ；while the protein expression of Bcl- 2，the levels of SOD and GPx were increased significantly ，and most above indexes in double-dose of gastradin group were better than regular-dose of gastrodin group （P＜0.05 or P＜0.01）. Compared with NC adenovirus group ，cell apoptosis rate of striatum ，protein expression of Bax ，Cleaved caspase- 3 and nNOS ，the levels of MDA and NO were increased significantly in NC adenovirus+methamphetamine group ；while the protein expression of Bcl- 2，the levels of SOD and GPx were decreased significantly （P＜0.01）. Compared with NC adenovirus+methamphetamine group ，cell apoptosis rate of striatum ，protein expression of Bax ，Cleaved caspase- 3 and nNOS ，the levels of MDA and NO were decreased significantly in NC adenovirus+ gastrodin group ；while the protein expression of Bcl- 2，the levels of SOD and GPx were increased significantly （P＜0.01）. Compared with NC adenovirus+gastrodin group ，cell apoptosis rate of striatum ，protein expression of Bax ，Cleaved caspase- 3 and nNOS，the levels of MDA and NO were increased significantly in nNOS adenovirus+gastrodin group ；while the protein expression of Bcl- 2，the levels of SOD and GPx were decreased significantly （P＜0.01）. CONCLUSIONS ：Gastrodin injection can protect rats against neurotoxic damage induced by methamphetamine ，and the effect is related to the inhibition of nNOS-mediated apoptosis and oxidative stress.