The causes of individual variation in behavior are often not well understood, and potential underlying mechanisms include both intrinsic and extrinsic factors, such as early environmental, physiological, and genetic differences. In an exploratory laboratory study, we raised three-spined sticklebacks (Gasterosteus aculeatus) under 4 different environmental conditions (simulated predator environment, complex environment, variable social environment, and control). We investigated how these manipulations related to behavior, brain physiology, and gene expression later in life, with focus on brain dopamine and serotonin levels, turnover rates, and gene expression. The different rearing environments influenced behavior and gene expression, but did not alter monoamine levels or metabolites. Specifically, compared to control fish, fish exposed to a simulated predator environment tended to be less aggressive, more exploratory, and more neophobic; and fish raised in both complex and variable social environments tended to be less neophobic. Exposure to a simulated predator environment tended to lower expression of dopamine receptor DRD4A, a complex environment increased expression of dopamine receptor DRD1B, while a variable social environment tended to increase serotonin receptor 5-HTR2B and serotonin transporter SLC6A4A expression. Despite both behavior and gene expression varying with early environment, there was no evidence that gene expression mediated the relationship between early environment and behavior. Our results confirm that environmental conditions early in life can affect phenotypic variation. However, the mechanistic pathway of the monoaminergic systems translating early environmental variation into observed behavioral responses was not detected.

中文翻译：

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饲养对行为，脑单胺和基因表达的影响在三刺的棘背鱼。

个体行为变化的原因通常不是很清楚，潜在的潜在机制包括内在和外在因素，例如早期的环境，生理和遗传差异。在一项探索性实验室研究中，我们在4种不同的环境条件（模拟的捕食者环境，复杂的环境，可变的社会环境和控制）下饲养了三棘刺背鱼（Gasterosteus aculeatus）。我们研究了这些操作如何与生活中的行为，大脑生理和基因表达相关联，重点关注脑中的多巴胺和5-羟色胺水平，周转率和基因表达。不同的饲养环境会影响行为和基因表达，但不会改变单胺水平或代谢产物。具体来说，与对照鱼相比，暴露于模拟捕食者环境中的鱼往往攻击性较小，探索性更大且更憎新生物；在复杂和多变的社会环境中饲养的鱼类的新恐惧症倾向较少。暴露在模拟的捕食者环境中倾向于降低多巴胺受体DRD4A的表达，复杂的环境会增加多巴胺受体DRD1B的表达，而可变的社会环境则倾向于增加5-羟色胺受体5-HTR2B和5-羟色胺转运蛋白SLC6A4A的表达。尽管行为和基因表达都随早期环境而变化，但是没有证据表明基因表达介导了早期环境和行为之间的关系。我们的结果证实，生命早期的环境条件会影响表型变异。然而，