Time-point changes of monoamine transporters' expressions in prefrontal cortex area of rats after morphine exposure

Objective: To study the changes of dopamine transporters (DAT) and serotonin transporter ( 5-HTT) expressions in brain prefrontal cortex (PFC)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 50mg. 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 prefrontal cortex (PFC)was selected and mounted on sliders. The gray mean levels of DAT and 5-HTT in selected area were investigated with in 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 PFC of the morphine group at different time points(P0.001); compared with the control group , the morphine group at all time points except M6 showed significant difference (P0.001), at the all time points are higher,M1 is highest. (2) For the gray mean levels of DAT , there was significant difference in the PFC of morphine group at all time points(P0.001) ; compared with the control group , the morphine group at all time points showed significant difference (P0.001) , at the M0、M1 are higher, but M6、M14 are descend,M21 again up; Conclusion: After withdrawal of chronic morphine exposure, DAT and 5-HTT density in the PFC are lower at initial and later stage , higher at middle stage ,witch suggests that the regulating of DAT and 5-HTT expression in PFC area may be involved in the development of opioid dependence.