| Objectives To explore the role of diazepam binding inhibitor (DBI) in morphine dependence. Methods (1)Thirty male Sprague-Dawley rats were randomly assigned to experiment group (n=20) and control group (n=10). The experiment group was re-classified into four subgroups based on the time of last morphine injection: 3-hour group (dependent group), 3-day withdrawal group, 6-day withdrawal group and 10-day withdrawal group, respectively. Rats in experiment group were intraperitoneally administrated with morphine, twice a day for ten days, in an ascending dosage schedule, from 5mg/kg per dose at the first day, to the 50mg/kg per dose at the tenth day increasing 5mg/kg per dose per day. Rats in control groups were injected with same volume saline. Conditioned place preference was observed on baseline, at day 5 and day 10 during the injection, at day 3, 6 and 10 after the end of treatment. Withdrawal signs, including teeth chattering(TC), wet dog shakes(WS), rearing, stretching, penis licking(PL), diarrhea, piloerection and weight loss(WL) were recorded at day 1, 3, 6 and 10 after the end of treatment. Data were analyzed using one-way ANOVA, followed by LSD.(2)At the time of 3 hours, 72 hours, 6 days and 10 days after the final injection, rats were scarified and cardio-perfused, and the brains were removed and sliced up coronarily. The sections including ventral tegmental area (VTA), nucleus accumben (NAc), the CA1 of hippocampus (HIPCA1), prefrontal cortex(PFC),amygdala (AMG), periaqueductal gray (PAG),Locus coeruleus (LC) were selected. The mRNA levels of DBI in the regions were estimated with in situ hybridization. Results (1)Among six groups, there were no difference in the times of rats' staying in white chamber on baseline. The time was significantly longer in experiment groups than in control group at day 5, day 10 after the beginning of the treatment and day 3, day 6 after the end of the treatment. However there were no statistically significant difference between 10-day withdrawal group and control group at day 10 after the end of the treatment.(2)The scores of total withdraw signs was significantly higher in 3-day withdrawal group, 6-day withdrawal group and 10-day withdrawal group than in control group at day 3 after the end of treatment. But at day 1 , day 6 and day 10 after the end of treatment, there were no significant difference between experiment groups and control group. (3) The mean levels of expression of the DBI in differentregions significantly increases in 3h group, reached the peak level at 3 day after the end of morphine administration group, then decreased. At the ten-day of discontinuation of treatment the expressed levels came to the baseline in VTA, NAc, HIPCA1, AMG and PAG. but in PFC it is still higher than control group. Conclusions (1) The chronic morphine treatment develop conditioned place preference, and rats expressed marked withdraw syndrome at day 3 after treatment. It suggests that the modeling of morphine dependence was successfully established. (2) The up-regulation of DBI mRNA following chronic morphine administration and withdrawal may be the one of molecular mechanism underlying opiate dependence and withdrawal. (3) In different brain regions at the same time-point of experiment group, in the regions including AMG, PFC, VTA and NAc, which are related to psychological dependence, the expressions of DBI mRNA are higher than AMG and LC, which are related to physical dependence. At the same time, the expressions of selected brain regions are related to CPP. It indicated that DBI may play a role not only in physical dependence but also in psychological dependence.
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