青龄大鼠和成龄大鼠在吗啡条件性位置偏爱和行为敏感化效应上的差异

目的 考察青龄大鼠在吗啡奖赏效应和行为激活效应上是否比成龄大鼠更加敏感.方法 使用条件化位置偏爱程序检验吗啡奖赏效应和行为敏感化效应,青龄雄性大鼠(出生后35d)和成龄雄性大鼠(出生后67d)每天接受盐水或吗啡(3mg/kg)注射,进行6d的位置条件化训练,同时记录条件化训练期间大鼠在伴药箱的水平运动量,训练结束24h后对条件性位置偏爱效应进行检测.结果 青龄大鼠没有形成吗啡条件性位置偏爱效应盐水组(20.89±31.14)s,吗啡组(90.75±27.91)s,P=0.15];成龄大鼠形成了吗啡条件性位置偏爱效应盐水组(31.5±41.24)s,吗啡组(266.13±32.26)s,P<0.01];成龄大鼠的吗啡条件性位置偏爱效应显著高于青龄大鼠(p<0.01).青龄吗啡组大鼠d3～d6的水平运动量均显著高于dl(P<0.05或P<0.01),成龄吗啡组大鼠d2～d6的水平运动量均显著高于d1(P<0.05或P<0.01);对吗啡给药大鼠进行二因素重复测量方差分析表明:年龄主效应不显著F_(1,14)=0.33,JP=0.57],年龄×处理交互作用不显著F_(5,70)=0.85,P=0.52].结论 青龄大鼠对吗啡的奖赏效应不如成龄大鼠敏感,但与成龄大鼠有着类似的行为敏感化效应.

Differential effects of morphine on conditioned place preference and locomotor activity in adult and adolescent rats

Objective To test whether adolescent rats are more sensitive than adult rats to morphine' s rewarding actions and locomotor activating effects. Methods Conditioned place preference(CPP) procedure was used to examine drug-induced reward and locomotor activity. Adolescent ( Postnatal day 35 ) and adult ( P67 ) male rats received either saline or morphine (3 mg/kg) for 6 days and the locomotor response in the drug paired chamber was recorded during conditioned training. CPP effects were tested 24h after the last training. Results In adolescent rats, morphine CPP effect was not present saline group (20. 89 ±31. 14) s, morphine group (90. 75 ± 27.91)s, P = 0. 15], however, morphine CPP effect occurred in adult ratssaline group (31.5 ± 41. 24) s, morphine group(266. 13 ± 32. 26) s, P < 0. 001 ]. Adult rats presented higher CPP score than adolescent rats(P < 0.001). The locomotor response was significantly higher in day 3 ～ 6 than day 1 in the adolescent treated with morphine (P<0.05 or <0. 01). The locomotor response was significantly higher in day 2-6 than day 1 in the adolescent treated with morphine(P<0. 05 or < 0. 01 ) .which suggested that both adolescent and adult rats exhibited similar behavioral sensitization to morphine administration. Two-way ANOVA indicated that the main effect of age was not significant(F_(1,14) =0. 33, P = 0. 57) ,the interaction effect of age x treat was not significant(F_(5,70) = 0.85, P = 0.52) .there was no age difference between adolescent and adult rats in behavioral sensitization effects. Conclusion Compared with adult rats, adolescent rats don' t present morphine CPP, but show the similar morphine behavioral sensitization.