Ritz M.C., Garcia J.M., Protz D., Rael A.-M., George F.R.
Department of Psychology & Psychiatry, and Center on Alcoholism, Substance Abuse & Addictions (CASAA), University of New Mexico, Albuquerque, NM 87131, USA.
Behav Pharmacol. 1994 Aug;5(4 And 5):521-531. doi: 10.1097/00008877-199408000-00013.
Genetic differences exist in whether animals find ethanol or other drugs positively reinforcing. Through the use of P, NP, HAD and LAD rats, animals selectively bred for high (P, HAD) or low (NP, LAD) ethanol consumption in a two-bottle choice procedure, the present results show that multiple factors determining ethanol consumption can be identified. Ethanol-preferring P rats consumed more ethanol across all conditions involving fixed ratio or progressive schedules than did non-preferring NP, preferring HAD or non-preferring LAD rats. In both non-preferring NP and preferring HAD rats, responding decreased similarly as fixed ratio size was increased. However, under a progressive ratio schedule, NP rats responded to higher break points than did HAD rats. In LAD rats, ethanol has not consistently been shown to be a reinforcer and these rats exhibited the lowest levels of responding for ethanol across all conditions. These findings extend the conditions under which P rats have been shown to consume substantial amounts of ethanol. In addition the results illustrate genetic differences with regard to the propensity of animals to maintain ethanol-reinforced behaviors under different schedules of intermittent reinforcement, and provide further evidence that ethanol drinking in a preference paradigm is not highly predictive of whether or to what extent ethanol may come to serve as a positive reinforcer. The results suggest that the phenomenon of ethanol drinking is a composite of at least three genetically independent factors governing different aspects of ethanol-seeking behavior: (1) a permissive factor allowing animals to readily overcome the aversive sensory effects of ethanol; (2) a reinforcement factor that determines whether a substance can come to serve as a positive reinforcer; and (3) a motivational factor related to the subjects' drive state with regard to drug seeking.
动物是否觉得乙醇或其他药物具有正性强化作用存在基因差异。通过使用P、NP、HAD和LAD大鼠，这些大鼠是在双瓶选择程序中针对高（P、HAD）或低（NP、LAD）乙醇消耗量进行选择性培育的，目前的结果表明，可以确定决定乙醇消耗量的多个因素。在所有涉及固定比率或累进程序的条件下，偏好乙醇的P大鼠比不偏好的NP、偏好的HAD或不偏好的LAD大鼠消耗更多的乙醇。在不偏好的NP大鼠和偏好的HAD大鼠中，随着固定比率大小的增加，反应同样减少。然而，在累进比率程序下，NP大鼠的反应断点比HAD大鼠更高。在LAD大鼠中，乙醇并未一直被证明是一种强化物，并且这些大鼠在所有条件下对乙醇的反应水平最低。这些发现扩展了已证明P大鼠会消耗大量乙醇的条件。此外，结果说明了动物在不同间歇性强化程序下维持乙醇强化行为的倾向方面的基因差异，并提供了进一步的证据，即在偏好范式中饮酒并不能高度预测乙醇是否或在多大程度上可能成为一种正性强化物。结果表明，饮酒现象是至少三个基因独立因素的综合，这些因素控制着觅酒行为的不同方面：（1）一个允许动物轻易克服乙醇厌恶感官效应的许可因素；（2）一个决定一种物质是否能成为正性强化物的强化因素；（3）一个与受试者对觅药的驱动状态相关的动机因素。
