Elmer G I, Meisch R A, Goldberg S R, George F R
Behavior Genetics Laboratory, National Institute on Drug Abuse, Baltimore, MD 21224.
Psychopharmacology (Berl). 1988;96(4):431-6. doi: 10.1007/BF02180019.
Previous studies of ethanol reinforcement in BALB/cJ and C57BL/6J mice have shown that over a range of concentrations oral ethanol appeared to serve as a reinforcer only for the C57BL/6J mice. In the previous studies BALB/cJ mice maintained rates of responding for ethanol that only slightly exceeded the rates maintained by the vehicle, water. However, the quantity of ethanol consumed with the continuous reinforcement schedule (fixed ratio one) may have led to pharmacologically significant effects, given the high sensitivity to ethanol of this genotype. The present study tested whether and to what extent ethanol would maintain responding under increasing fixed ratio size in these two strains of mice at ethanol concentrations of 0%, 8%, and 16% (w/v). For the C57BL/6J mice, as fixed-ratio size increased from 1 to 2, 4, and 8, there were almost directly proportional increases in response rate at ethanol concentrations of 8% and 16% (w/v), but not at 0%. Post-session blood ethanol levels confirmed intake of pharmacologically significant quantities. The volume consumed per unit of body weight decreased as fixed-ratio size increased. For the BALB/cJ mice, at no condition did ethanol maintain responding at levels that significantly exceeded vehicle maintained responding. BALB/cJ mice did not differ from C57BL/6J mice as fixed-ratio size was increased during vehicle conditions. These results, along with earlier findings, demonstrate that ethanol can serve as a reinforcer for C57BL/6J mice but not in BALB/cJ mice over a range of schedule conditions. They further support the conclusion that genotype is an important determinant of ethanol reinforced behavior.
先前对BALB/cJ和C57BL/6J小鼠乙醇强化作用的研究表明，在一定浓度范围内，口服乙醇似乎仅对C57BL/6J小鼠起到强化物的作用。在先前的研究中，BALB/cJ小鼠对乙醇的反应率仅略高于溶剂（水）维持的反应率。然而，鉴于该基因型对乙醇高度敏感，连续强化程序（固定比率为1）下消耗的乙醇量可能已产生药理学上的显著影响。本研究测试了在0%、8%和16%（w/v）的乙醇浓度下，这两种品系的小鼠在固定比率增加时，乙醇是否以及在多大程度上会维持反应。对于C57BL/6J小鼠，当固定比率从1增加到2、4和8时，在8%和16%（w/v）的乙醇浓度下，反应率几乎呈直接比例增加，但在0%浓度下并非如此。实验后血液中的乙醇水平证实摄入了具有药理学意义的量。每单位体重消耗的体积随着固定比率的增加而减少。对于BALB/cJ小鼠，在任何情况下，乙醇维持的反应水平均未显著超过溶剂维持的反应水平。在溶剂条件下，随着固定比率的增加，BALB/cJ小鼠与C57BL/6J小鼠没有差异。这些结果与早期发现一起表明，在一系列程序条件下，乙醇可作为C57BL/6J小鼠的强化物，但不能作为BALB/cJ小鼠的强化物。它们进一步支持了基因型是乙醇强化行为的重要决定因素这一结论。
