[Dopamine D2 receptor and transportor [corrected] in the medial prefrontal contex of morphine-induced conditioned place preference in Sprague-Dawley rats].
OBJECTIVE
To investigate the expression of dopamine D2 receptors (D2R) and dopamine transportors (DAT) located in the medial prefrontal contex (mPFC) in high and low conditioned place preference (CPP) rats, and to unveil the possible mechanism leading to different CPP susceptibilities.


METHODS
One hundred and sixty male Sprague-Dawley rats were randomly assigned into an experiment group (n = 130) and a control group (n = 30). The experiment group was re-classified into 2 groups according to CPP values:high preference group (HP group) and low preference group (LP group). According to the execution time-points after the last administration, the HP and LP group was classified into a 3-hour group (3 h), a 72-hour group (J3d), and a 14-day group (J14d), respectively. At 3 hours, 72 hours, and 14 days after the final injection, rats were killed and cardio-perfused, and the brains were removed and sliced up coronarily. The mRNA levels of D2R and DAT in mPFC were determined with in situ hybridization.


RESULTS
There were no significant differences of pretest scores staying at the non-preference chamber among the groups(P = 0.470). However, the test scores of the CPP time stayed at pretest natural preference in the HP group were significantly higher than those of the LP group(P = 0.000). In 3h, J3d, and J14d groups,the expressions of D2R mRNA in the HP group (125.43 +/- 2.90 approximately 142.92 +/- 3.32) were lower than those of LP group (122.25 +/- 2.20 approximately 136.67 +/-5.39) (P = 0.000). In 3h and J3d,the expressions of DAT mRNA in the HP group (157.00 +/- 3.55 approximately 145.15 +/- 3.69) were significantly lower than those of the LP group (150.69 +/- 3.12 approximately 138.84 +/- 3.99) (P = 0.000). In J14d, there were no differences among 3 groups in mPFC (P = 0.458).


CONCLUSIONS
D2R and DAT may be correlated closely and underlie the different susceptibilities to morphine induced CPP.
Chen
Hong-xian
HX
Mental Health Institute, Second Xiangya Hospital, Central South University, Changsha 410011, China. chxian1971@163.com
Ye
Min-jie
MJ
Wang
Ying
Y
Zhang
Rui-ling
RL
Hao
Wei
W
Li
Chang-qi
CQ
D000818:Animals; D003213:Conditioning, Psychological / Q000187:drug effects*; D004198:Disease Susceptibility / Q000378:metabolism; D050483:Dopamine Plasma Membrane Transport Proteins / Q000096:biosynthesis* / Q000235:genetics; D008297:Male; D009021:Morphine Dependence / Q000378:metabolism*; D017397:Prefrontal Cortex / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D017448:Receptors, Dopamine D2 / Q000096:biosynthesis* / Q000235:genetics
D050483:Dopamine Plasma Membrane Transport Proteins; D012333:RNA, Messenger; D017448:Receptors, Dopamine D2