TIME-POINT CHANGES OF MONOAMINE TRANSPORTERS′ EXPRESSION IN NUCLEUS ACCUMBEN AREA OF RATS AFTER MORPHINE EXPOSURE

Objective:To study the changes of dopamine transporters(DAT) and serotonin transporter(5-HTT) expressions in brain nucleus accumben (NAc)area of rats with chronic morphine dependence at different time points after withdrawal. Methods:Fifty male Sprague-Dawley rats were randomly assigned into experimental(n=25,morphine) and control(n=25, saline) groups. The experimental group was administered morphine(ip) twice a day with an initial dose of 5 mg·kg~ -1 each time,and then increased gradually day by day,till 50 mg[DK]·[DK]kg~ -1 each time at day 10. Accordingly the control group was injected with saline of the same volume. At the time point of day 0,1,6,14, 21(M0, M1,M6,M14,M21) after injection termination,rats in both groups were perfused and the brains were removed and cut coronally at the same time. The sections including nucleus accumben (NAc) was selected and mounted on sliders. The gray mean levels of DAT and 5-HTT in selected area were investigated within immunity histochemistry and the results were compared according to the identical time points. Results: (1) For the gray mean levels of 5-HTT,significant difference was observed in the NAc of the morphine group at different time points(P0.001); compared with the control group,the morphine group at all time points except M21showed significant difference(P0.001); morphine group at the M0, M1 had higher gray mean levels of 5-HTT,and at M6、M14、M21 were lower. (2) For the gray mean levels of DAT,there was significant difference in the NAc of morphine group at all time points(P 0.001), and significant difference was also observed compared with the control group(P0.001), with the morphine group at all time points having higher levels,especially at M0. Conclusion:After withdrawal of chronic morphine exposure, DAT and 5-HTT density in the NAc are lower at initial stage, and increase at later stage, which suggests that the regulating of DAT and 5-HTT expression in NAc area may be involved in the development of opioid dependence.