应激和环境对吗啡暴露大鼠的电生理和行为学影响的研究

目的:研究平台应激、急性吗啡暴露对4周龄和10周龄♂W istar大鼠海马CA1区突触可塑性及空间记忆的影响以及研究丰富环境对大鼠学习记忆、吗啡诱导的条件性位置偏爱(cond itioned p lace preference,CPP)及海马CA1区突触可塑性的影响。方法:电生理实验(在体和离体)和行为学方法(水迷宫和CPP实验),统计采用方差分析(ANOVA)和t检验。结果与结论:(1)慢性应激和/或急性吗啡暴露分别对4周龄和10周龄这两个年龄段的LTP和LTD具有不同作用,存在明显的年龄差异。(2)急性平台应激损害4周龄和10周龄大鼠的记忆,但年龄差异没有显著性;慢性平台应激对10周龄大鼠记忆起易化作用,对4周龄没有明显的影响。(3)急性吗啡暴露(2 mg.kg-1)对4周龄大鼠的记忆有损害作用,而对10周龄大鼠的记忆没有影响。(4)急性应激加吗啡损害了4周龄大鼠的记忆保持,而对10周龄大鼠的记忆保持无影响;慢性应激加吗啡对4周龄大鼠的记忆保持无影响,对10周龄大鼠的记忆保持有易化作用。(5)丰富环境可以增强大鼠的空间学习和记忆能力,增强了吗啡诱导的CPP可能与学习和记忆能力的提高有关;同时,丰富环境对吗啡依赖所致的突触可塑性的损害有保护作用。丰富环境能逆转早期应激所产生的对学习记忆和突触可塑性的损害。

THE STUDY OF IMPACT OF STRESS AND ENVIRONMENT ON ELECTROPHYSIOLOGY AND BEHAVIOR CHANGES IN MORPHINE -EXPOSED RATS

Objective: To study the effect of stress and acute morphine exposure on synaptic plasticity of hippocampal CA1 area and spatial memory in rats of different ages;to study the effects of enriched environment(EE) on spatial learning and memory and morphine induced conditioned place preference(CPP) of Wistar rats,to explore if EE can affect synaptic plasticity on normal and addicted rats.Methods: Electrophysiological technique in vivo and in vitro and behavioral test including Morris water maze and CPP were used in this study.Statistical analysis was made using ANOVA or Student's t-test. Results and conclusions:(1) Chronic stress and morphine had different effects on LTP and LTD in(4-and)-10-week-old rats and it showed significant difference between the two age groups of rats.LTP and LTD were facilitated in chronic stress and morphine group of 4-week-old rats;LTP was impaired and LTD was completely inhibited in the same group of 10-week-old rats.(2) Acute EP stress induced impairment of memory retention in 4-or 10-week-old rats,respectively,but it did not differ between 4-week-old rats and 10-week-old rats.Chronic EP stress induced enhancement of memory retention in 10-week-old rats and had no effect on memory retrieval in 4-week-old rats.(3) Morphine at the dose of 2 mg·kg~(-1) induced impairment of memory retention in 4-week-old rats and had no effect on memory retention in 10-week-old rats.(4) Acute EP stress and morphine induced impairment of memory retention in 4-week-old rats and had no effect on memory in 10-week-old rats.Chronic stress and morphine had no effect on memory retention in 4-week-old rats and induced enhancement of memory retention in 10-week-old rats.(5)EE enhanced morphine induced CPP,possibly due to the increased spatial learning and memory;and the synaptic plasticity impairments induced by morphine addiction can be attenuated by EE,suggest that EE may be helpful in protecting synaptic plasticity from opioids induced impairments.EE can reverse the impairment of early stress on spatial learning and synaptic plasticity.