The Effectiveness Of Buprenorphine In Combination With Scopolamine And Promethazine On Conditioned Place Preference And Spatial Memory And Its Related Mechanisms In SD Rats

Part I To Study the Rewarding Effects of DifferentBuprenorphine Doses on the Conditioned PlacePreference in SD RatsObjectiveTo explore the rewarding effects of different buprenorphine doses in a conditioned place preference (CPP) paradigm.MethodsForty male Sprague-Dawley rats were randomly assigned to 4 groups: low-dose group, middle-dose group, high-dose group and saline group. Correspondently they were treated with 0.1mg/kg, 0.3mg/kg, 1.0mg/kg buprenorphine and saline intraperitonealy. All the rats were trained in the conditioned place preference paradigm for 7-day session and the CPP was tested on the day 8.Results(1) After 7-day training the time spent in the buprenorphine-paired side by the rats in the middle-dose group and high-dose group are (260.40±63.89) seconds and (257.10±48.79) seconds respectively, significantly longer than the pre-training time (497.90±73.87) seconds and (321.00±73.70) seconds, respectively (t=6.91, 4.04; P=0.000, 0.003).(2) The extended time in the drug-paired side spent by the rats in the middle-dose group is (237.50±108.64) seconds, significantly longer than the extended time (63.90±49.95) seconds by the rats in the high-dose group (P<0.01) .Conclusion(1) SD rats in both Middle-dose and high-dose buprenorphine can to develop CPP in the SD rats. (2) Middle-dose buprenorphine has the better rewarding effects than other buprenorphine groups. Part II The Effectiveness of Buprenorphine inCombination with Scopolamine and Promethazine onConditioned Place Preference and Dopamine D₂ ReceptormRNA Expression in Some Brain Regions in SD RatsObjectiveTo explore the effects of buprenorphine, scopolamine and promethazine and their different combinations on CPP and dopamine D₂ receptor mRNA expression in some brain regions in SD ratsMethodsOne hundred and sixty-one male Sprague-Dawley rats were randomly assigned to 9 groups: buprenorphine, scopolamine, promethazine, buprenorphine plus scopolamine, buprenorphine plus promethazine, buprenorphine plus scopolamine and promethazine (abbrev as "bup+sco+pro"), scopolamine plus promethazine, morphine and saline groups respectively. All the 9 groups were trained by using the conditioned place preference (CPP) paradigm for 7 days and then were tested on day 8. After all the behavioral tests, thirty-six rats, randomly selected from "bup+sco+pro" group, buprenorphine group, mophine group and saline group, were decapitated. Consequently the brain regions were dissected for analyzing the dopamine D₂ mRNA expression by means of in-situ hybridization . Results(1) The rats in the five groups treated with buprenorphine alone or in combination with scopolamine and/ or promethazine and morphine developed CPP significantly. (2) The extended time spent by the rats in the "bup+sco+pro" group is (378.64±120.76) seconds, significantly longer than those in the buprenorphine group (P=0.025 < 0.05 ) , buprenorphine plus scopolamine group (P=0.005<0.05) , buprenorphine plus promethazine group (P=0.013<0.05), but similar to those by the rats in the morphine group (419.83±146.44) seconds (P=0.223>0.05) . (3) In brain areas such as acbSH, PFC and CeA, the dopamine D₂ receptor mRNA expression in the "bup+sco+pro" group is lower than those of rats in the buprenorphine and saline groups while there is no significant different compared with those in morphine group. However, there are no significant differences in other areas in the four groups.Conclusions(1) The combination use of buprenorphine plus scopolamine and promethazine can induce SD rat to develop significant CPP. (2) Scopolamine and promethazine may act synergistically to enhance psychological dependence of buprenorphine, and the most likely mechanism is by means of increasing the release of dopamine in the meso-limbic dopamine system. Part III The Effectiveness of Buprenorphine inCombination with Scopolamine and Promethazine onSpatial Memory and CHAT and Synaptsin I mRNAExpression in SD RatsObjectiveTo explore the effects of buprenorphine, scopolamine and promethazine and their different combinations on the spatial memory and CHAT and synaptsin I mRNA expression in some brain regions in SD rats MethodsThe protocol for the treatment of experiment animals mentioned in part two is used in the part. After completing the CPP training and test, The Morris water maze training was conducted in three consecutive days. After behavioral test, thirty-six rats, randomly selected from "bup+sco+pro" group, buprenorphine group, mophine group and saline group, were decapitated. Consequently the brain regions were dissected for analyzing the CHAT and synaptsin I mRNA expression by means of in-situ hybridization and immunohistochemistry.Results(1) The escape latency of the rats in "bup+sco+pro"group is (48.67±14.47) seconds, significantly longer than those in the other groups (P< 0.05) . But the target quadrant and the times of crossing the plateau for "bup+sco+pro" group is (46.42±10.08) seconds and (3.58±1.31) times respectively, significantly shorter than those in all other groups (P <0.05) . (2) In brain areas of CA1 and PFC, the choline acetyl transferase (CHAT) mRNA expression of the rats in "bup+sco+pro"group is significantly lower than those in all other groups (P<0.05) . But in the spared brain areas, there are no difference between all the groups (P<0.05). (3) In brain areas of CA1 and PFC, the synaptsin I mRNA expression of rats in the "bup+sco+pro"group is significantly lower than those in morphine group, buprenorphine group and saline group ( P < 0.05 ) . But in VTA, the expression for "bup+sco+pro"group and morphine group is significantly higher than those for buprenorphine group and saline group (P<0.05) .Conclusions (1)The combination use of buprenorphine with scopolamine and promethazine has synergistic effect on damage of the spatial memory in rats. (2) Buprenorphine plus scopolamine and promethazine may act synergistically to decrease the spatial memory in SD rats. Scopolamine and promethazine may enhance the buprenorphine-induced memory deficits, possibly due to the decreased CHAT and synaptsin I mRNA expression in some brain areas.