Ator N A, Griffiths R R
Pharmacol Biochem Behav. 1983 Dec;19(6):993-1003. doi: 10.1016/0091-3057(83)90406-9.
Two experiments were conducted in which responding maintained by nicotine and cocaine was studied under two different schedules of drug delivery. In Experiment 1, nicotine (0.01-0.32 mg/kg IV) was available under a fixed-ratio 2 timeout 15 sec reinforcement schedule. When nicotine was substituted for cocaine or saline, dose-dependent differences in self-administration were evident across the first five sessions, resulting in an inverted U-shaped dose-effect curve. With continued exposure to each nicotine dose, however, number of injections generally stabilized at levels not very different, if at all, from saline; and the terminal dose-effect functions generally were low and flat. In Experiment 2, nicotine (0.01-0.56 mg/kg IV) was available under a fixed-interval 5 min timeout 60 sec reinforcement schedule. Response rates were considerably lower and response patterning was less likely to be scalloped than when responding was maintained by either cocaine or food, but number of injections was higher than those maintained by saline. When fixed-interval value was varied, number of nicotine reinforcements remained low and virtually constant, but number of food reinforcements increased as the fixed interval decreased. The present results, along with those from previous studies, suggest that the ability of nicotine to serve as a reinforcer appears to be strongly influenced by the conditions of drug availability, perhaps more so than for other drugs of abuse.
进行了两项实验，研究在两种不同的药物给药方案下，由尼古丁和可卡因维持的反应。在实验1中，尼古丁（0.01 - 0.32毫克/千克静脉注射）可在固定比率2、超时15秒的强化方案下获得。当用尼古丁替代可卡因或生理盐水时，在前五个实验环节中，自我给药的剂量依赖性差异明显，形成了倒U形剂量效应曲线。然而，随着持续接触每种尼古丁剂量，注射次数通常稳定在与生理盐水相比差异不大（如果有差异的话）的水平；最终的剂量效应函数通常较低且平缓。在实验2中，尼古丁（0.01 - 0.56毫克/千克静脉注射）可在固定间隔5分钟、超时60秒的强化方案下获得。与由可卡因或食物维持反应时相比，反应率相当低，反应模式不太可能呈扇形，但注射次数高于由生理盐水维持反应时的次数。当改变固定间隔值时，尼古丁强化的次数仍然很低且几乎保持不变，但食物强化的次数随着固定间隔的缩短而增加。目前的结果，连同先前研究的结果，表明尼古丁作为强化物的能力似乎受到药物可得条件的强烈影响，可能比其他滥用药物的影响更大。
