Ristuccia Robert C, Spear Linda P
Department of Psychiatry, Division of Developmental Neuroscience, Columbia University, New York, New York 11032, USA.
Alcohol Clin Exp Res. 2008 Oct;32(10):1807-15. doi: 10.1111/j.1530-0277.2008.00752.x. Epub 2008 Jul 24.
Despite the fact that adolescent rats have repeatedly been found to consume more ethanol than adult rats in a variety of ethanol access paradigms, the exact cause of the increase in ethanol consumption during adolescence is not known. One possibility is that age differences in sensitivity to ethanol's rewarding effects may contribute to the elevated intake seen among adolescents. Human studies have shown that autonomic effects of ethanol, particularly ethanol-induced tachycardia, are correlated with the positive hedonic properties of the drug and, hence, may serve as a biomarker for reward.
In this experiment, a limited-access self-administration paradigm was used to examine the autonomic effects of ethanol in outbred male adolescent and in adult Sprague-Dawley rats under circumstances likely to reveal the rewarding value of ethanol.
The results indicated that voluntary ethanol consumption was greater in adolescent than adult rats and that only adolescents consumed enough of the saccharin-sweetened ethanol solution to show a tachycardic effect greater than that seen in response to saccharin alone.
To the extent that these tachycardic properties of ethanol are associated with the rewarding/hedonic properties of ethanol as previously reported in humans, these findings support the suggestion that adolescent animals may have found the ethanol-containing solution to be more rewarding than the saccharin solution. A similar effect was not seen in adults, findings consistent with the notion that adult rats may not consume enough ethanol under these circumstances to experience its positive rewarding properties.
尽管在多种乙醇摄入模式下，多次发现青春期大鼠比成年大鼠摄入更多乙醇，但青春期乙醇摄入量增加的确切原因尚不清楚。一种可能性是，对乙醇奖赏效应的敏感性存在年龄差异，这可能导致了青春期大鼠乙醇摄入量的增加。人体研究表明，乙醇的自主效应，尤其是乙醇诱发的心动过速，与该药物的积极享乐特性相关，因此可能作为奖赏的生物标志物。
在本实验中，采用有限接触自我给药模式，在可能揭示乙醇奖赏价值的情况下，检测杂种雄性青春期大鼠和成年斯普拉格-道利大鼠体内乙醇的自主效应。
结果表明，青春期大鼠的乙醇自愿摄入量高于成年大鼠，且只有青春期大鼠摄入了足够量的糖精加甜乙醇溶液，从而表现出比单独摄入糖精时更大的心动过速效应。
鉴于乙醇的这些心动过速特性与先前在人体中报道的乙醇奖赏/享乐特性相关，这些发现支持了以下观点：青春期动物可能发现含乙醇溶液比糖精溶液更具奖赏性。在成年大鼠中未观察到类似效应，这一结果与成年大鼠在这些情况下可能未摄入足够乙醇以体验其积极奖赏特性的观点一致。
