Creation Of Heroin-induced Conditioned Place Preference In Rats And The Effect PCPA Exerting

ObjectiveThe objective of the present study was to construct video track conditioned place preference(CPP) experimental system in rats and set up heroin-induced CPP. Tryptophan hydroxylase inhibitor PCPA was used to exhaust the center nerve system(CNS) 5-HT and heroin-induced CPP in rats were performed, on this basis we search for the variation of heroin dependence formation and relapse in the condition CNS 5-HT transmission dysfunction.Materials and methods1 System constructionThe video track CPP experimental system in rats was composed of shuttle box, a sound-proof container, vedio apparatus and a computer. The video was analyzed using Mice Track software.2 Animals72 male Sprague-Dawley rats were used, in which 24 rats divided in three groups participated in heroin-induced CPP while the rest divided in six groups undertook the research of PCPA treatment.3 Methods3.1 Heroin induced place-preference conditioning schedule consisted of three phases.(1) Conditioning phase, blocking partition were used to segregate the gray and black box, during which two groups of rats were treated for 2 consecutive with alternate injection of heroin (0. 5mg and Img per kg body weight in a volume of 3ml per kg body weight, i.p.) or saline one day for 6 days. Conditioning sessions were carried out over a 30min period immediately after injection. Rats were confined to the gray compartment after heroin injection and to the black compartment after saline injection. The control were offered saline(3ml per kg body weight, i.p.) before confinement to either compartment.(2) Testing phase, during which video was captured and tests of conditioning were performed as follows: the passage partitions were used for rats to freely access each compartment 20min, 24h after the final conditioning session and 10 days extinction phase.(3) Giving a mark of abstinent symptom, three groups of rats were administrated naloxone and undertook precipitated abstinent scores.3. 2 To investigate the effects of PCPA on heroin-induced CPP, PCPA with fixed dosage (0mg/kg> 100mg/kg> 300mg/kg) were administered to rats by i.p. for 3 days before conditioning and on the extinction day 7,8,9. Tests of rats' movement were conducted 24h after the final conditioning session and 10 days extinction phase to observe CPP formation and extinction respectively. The content of 5-HT in the platelet was determined according to the procedure of the Serotonin RIA Kit after CPP observation.4 Data analysisThe sojourn time in the gray compartment, the total distance rats moved, crossing times between the two compartments, the score of withdrawal symptom and the content of the 5-HT in platelet were obtained. Statistical analysis methods included Kruskal-Wallis test, Bonferronimulticomparison, Wilcoxcn signed rank test, one-way ANOVA , LSD multicomparison and Kendall' s tua-b bibariate correlations test.Results1 The potency of the systemRats moved freely in the shuttle box in a quiet, dim environment. Data were objectively obtained by analyzing the video using Mice Track software, which is flexible and can analyze several parameters simultaneously.2 Heroin-induced CPP foundation, extinction and locomotion changes in rats2.1 Heroin-induced CPP foundation and extinction24h after conditioning, the sojourn time of the two groups of rats conditioning with heroin in the gray compartment was significantly longer than control. 10 days passby, two heroin treated groups rats remained the preference. The sojourn time in gray compartment after extinction was significantly longer than before.2. 2 The movement changes after heroin-induce CPP creation and extinction in rats24h after the final conditioning session and over the 10-day extinction phase, the distance and crossing times had no difference in three groups of tats.2. 3 Correlation between sojourn time and distance in the gray compartment and crossing timesThere was strong correlation between the total moved distance and crossing times (r=0. 787, P<0. 001); while the...