Objective   To explore the expressions of gastrin (Gas) and 5-hydroxy tryptamine (5-HT) in the gastric antrum of rats who go through heroin withdrawal and then relapse.   Methods   A total of 35 adult male SD rats were randomly divided into 3 groups

normal control group (n=5)

saline control group (n=15) and experiment group (n=15). Experiment group was subdivided into heroin withdrawal group (n=5)

methadone detoxication group (n=5) and heroin relapse group  (n=5). All animals from experimental group were given injections of 3 mg/kg heroin at the first day

twice per day

then with an increase of 3 mg/kg every day for another 8 d and then followed a boost injection of 0.8 mg naloxone to establish heroin withdrawal model. Then the left 10 rats of the experimental group received a continued decrease injection of methadone for 6 d (5

4

3

2

1 and 0.5 mg/kg) to establish methadone detoxication rats. The left 5 rats were injected with heroin again from 9 to 3 mg/kg for 7 d with the dose decreased every day by 1 mg/kg. All rats from experimental group were sacrificed after the establishment of corresponding models.  Immunohistochemical SABC and image analysis were performed to detect the expressions of Gas and 5-HT.   Results   The expressions of Gas and 5-HT were increased during heroin withdrawal and relapse in rat antrum. Compared with normal control and saline control

heroin withdrawal and relapse group had more intense immunohistochemical staining

lower mean grey scale and more Gas and 5-HT positive cells (P0.05). There was no significant difference in the mean grey scale and positive cells counts of Gas and 5-HT (P0.05) in methadone detoxication group when compared with normal and saline control.   Conclusion   Gas and 5-HT show a trend of increased expression in rat antrum during withdrawal

and withdrawal and relapse

suggesting that they participate in the anti-heroin process. After methadone detoxication

the expressions of Gas and 5-HT were close to normal levels

which indicating the function of antrum turns to normal.