Maccioni Paola, Bratzu Jessica, Lobina Carla, Acciaro Carla, Corrias Gianluigi, Capra Alessandro, Carai Mauro A M, Agabio Roberta, Muntoni Anna Lisa, Gessa Gian Luigi, Colombo Giancarlo
Neuroscience Institute, Section of Cagliari, National Research Council of Italy, I-09042 Monserrato (CA), Italy.
Department of Physics, University of Cagliari, I-09042 Monserrato (CA), Italy.
Physiol Behav. 2022 May 15;249:113771. doi: 10.1016/j.physbeh.2022.113771. Epub 2022 Mar 2.
Living in an enriched environment (EE) produces a notable impact on several rodent behaviors, including those motivated by drugs of abuse. This picture is somewhat less clear when referring to alcohol-motivated behaviors. With the intent of contributing to this research field with data from one of the few rat lines selectively bred for excessive alcohol consumption, the present study investigated the effect of EE on operant oral alcohol self-administration in Sardinian alcohol-preferring (sP) rats. Starting from Postnatal Day (PND) 21, male sP rats were kept under 3 different housing conditions: impoverished environment (IE; single housing in shoebox-like cages with no environmental enrichment); standard environment (SE; small colony cages with 3 rats and no environmental enrichment); EE (large colony cages with 6 rats and multiple elements of environmental enrichment, including 2 floors, ladders, maze, running wheels, and shelter). From PND 60, rats were exposed to different phases of shaping and training of alcohol self-administration. IE, SE, and EE rats were then compared under (i) fixed ratio (FR) 4 (FR4) schedule of alcohol reinforcement for 20 daily sessions and (ii) progressive ratio (PR) schedule of alcohol reinforcement in a final single session. Acquisition of the lever-responding task (shaping) was slower in EE than IE and SE rats, as the likely consequence of a "devaluation" of the novel stimuli provided by the operant chamber in comparison to those to which EE rats were continuously exposed in their homecage or an alteration, induced by EE, of the rat "emotionality" state when facing the novel environment represented by the operant chamber. Training of alcohol self-administration was slower in EE than IE rats, with SE rats displaying intermediate values. A similar ranking order (IE>SE>EE) was also observed in number of lever-responses for alcohol, amount of self-administered alcohol, and breakpoint for alcohol under FR4 and PR schedules of reinforcement. These data suggest that living in a complex environment reduced the reinforcing and motivational properties of alcohol in sP rats. These results are interpreted in terms of the reinforcing and motivational properties of the main components of EE (i.e., social interactions, physical activities, exploration, novelty) substituting, at least partially, for those of alcohol.
生活在丰富环境（EE）中会对多种啮齿动物行为产生显著影响，包括那些由滥用药物引发的行为。当涉及到由酒精驱动的行为时，情况就有些不太清晰了。为了通过少数几种因过度饮酒而被选择性培育的大鼠品系之一的数据为该研究领域做出贡献，本研究调查了EE对撒丁岛嗜酒（sP）大鼠操作性口腔酒精自我给药的影响。从出生后第21天（PND 21）开始，雄性sP大鼠被饲养在3种不同的饲养条件下：贫瘠环境（IE；单只饲养在类似鞋盒的笼子里，没有环境丰富设施）；标准环境（SE；小群体笼子，3只大鼠，没有环境丰富设施）；EE（大群体笼子，6只大鼠，有多种环境丰富元素，包括两层、梯子、迷宫、跑轮和庇护所）。从PND 60开始，大鼠接受酒精自我给药的不同阶段的塑形和训练。然后在以下条件下比较IE、SE和EE大鼠：（i）固定比率（FR）4（FR4）酒精强化时间表，每天进行20次实验；（ii）在最后一次单次实验中采用渐进比率（PR）酒精强化时间表。EE大鼠获得杠杆反应任务（塑形）的速度比IE和SE大鼠慢，这可能是由于与EE大鼠在其饲养笼中持续接触的刺激相比，操作性实验箱提供的新刺激出现了“贬值”，或者是由于EE导致大鼠面对操作性实验箱所代表的新环境时“情绪性”状态发生了改变。EE大鼠的酒精自我给药训练比IE大鼠慢，SE大鼠的表现处于中间水平。在FR4和PR强化时间表下，在酒精的杠杆反应次数、自我给药酒精量和酒精的断点方面也观察到类似的排序顺序（IE>SE>EE）。这些数据表明，生活在复杂环境中会降低sP大鼠对酒精的强化和激励特性。这些结果可以从EE的主要成分（即社交互动、体育活动、探索、新奇性）的强化和激励特性至少部分替代酒精的强化和激励特性的角度来解释。
