Brenes Juan C, Padilla Michael, Fornaguera Jaime
Neuroscience Research Program, University of Costa Rica, Costa Rica.
Behav Brain Res. 2009 Jan 30;197(1):125-37. doi: 10.1016/j.bbr.2008.08.014. Epub 2008 Aug 22.
Our previous work has shown that male Sprague-Dawley rats reared in social isolation, standard housing and environmental enrichment differ in their spontaneous open-field activity and in some neurobehavioral depressive-like parameters. Here, we extended this evidence by using a shorter postweaning rearing period (1 month) and including additional evaluations. First, in order to obtain a better characterization of the exploratory strategies among rearing conditions we analyzed in detail the spontaneous activity at the first minute and during the 10-min session. Second, we asked whether the changes in open-field activity were related with basal anxiety levels in the elevated plus-maze. Third, behavior in the forced-swimming test was analyzed and afterward, the tissue levels of hippocampal norepinephrine and serotonin were assessed. The possible relationship between neurotransmitters and forced-swimming behavior were explored through correlation analyses. We found that rearing conditions (i) differed on locomotor habituation and on sensory-motor exploration at the first minute and during the 10-min session without modifying the plus-maze behavior; (ii) affected differentially the grooming time, its sequential components, and the relationship between grooming and locomotor parameters; (iii) modified forced-swimming behavior and the hippocampal concentration of norepinephrine, serotonin, and its turnover; and (iv) produced different correlation patterns between both neurotransmitters and forced-swimming behaviors. Overall, environmental enrichment accelerated open-field habituation and led to behavioral and neurochemical antidepressant-like effects. In contract, isolation rearing strongly impaired habituation and simple information processing, but showed marginal effects on depressive-like behavior and on hippocampal neurochemistry. The current results suggest that differential rearing is not only a useful procedure to study behavioral plasticity or rigidity in response to early experience, but also to modeling some developmental protective or risk factors underlying depressive disorders.
我们之前的研究表明，在社会隔离、标准饲养和环境丰富条件下饲养的雄性Sprague-Dawley大鼠，其自发旷场活动以及一些神经行为抑郁样参数存在差异。在此，我们通过使用较短的断奶后饲养期（1个月）并纳入额外评估来扩展这一证据。首先，为了更好地描述不同饲养条件下的探索策略，我们详细分析了第1分钟和10分钟测试期间的自发活动。其次，我们探究旷场活动的变化是否与高架十字迷宫中的基础焦虑水平相关。第三，分析了强迫游泳测试中的行为，随后评估了海马中去甲肾上腺素和5-羟色胺的组织水平。通过相关性分析探索了神经递质与强迫游泳行为之间的可能关系。我们发现饲养条件（i）在第1分钟和10分钟测试期间的运动习惯化和感觉运动探索方面存在差异，但未改变十字迷宫行为；（ii）对梳理时间、其顺序成分以及梳理与运动参数之间的关系有不同影响；（iii）改变了强迫游泳行为以及海马中去甲肾上腺素、5-羟色胺的浓度及其周转率；（iv）在两种神经递质与强迫游泳行为之间产生了不同的相关模式。总体而言，环境丰富加速了旷场习惯化，并产生了行为和神经化学抗抑郁样效应。相比之下，隔离饲养严重损害了习惯化和简单信息处理，但对抑郁样行为和海马神经化学的影响较小。当前结果表明，差异饲养不仅是研究对早期经验的行为可塑性或刚性的有用方法，也是模拟抑郁症潜在的一些发育保护或风险因素的有用方法。
