Long-term cocaine self-administration under fixed-ratio and second-order schedules in monkeys
Long-term cocaine self-administration under fixed-ratio and second-order schedules in monkeys
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DOI：
10.1007/s00213-006-0665-z
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发表时间：
2007-04-01
影响因子：
3.4
通讯作者：
Nader, Michael A.
中科院分区：
文献类型：
--
作者：
Czoty, Paul W.;Reboussin, Beth A.;Nader, Michael A.
对啮齿动物的研究表明，增加对可卡因的接触会导致单位时间内药物摄入量的增加。目的本研究描述了在不同的可卡因可得性条件下，猴子可卡因自我给药的长期变化与数量和质量的关系。材料与方法恒河猴（n=6/组）按固定比率（FR） 30自用可卡因（每次注射0.2 mg/kg） 3小时，每周连续两天，连续1年，或按固定比率（FR） 10（固定间隔3分钟：S）每天0.2 mg/kg注射可卡因。18周后，每周进行一次探针会话，在不同刺激存在下，反应在固定间隔（FI） 30分钟的时间表下保持。结果3只受试者的每周可卡因摄入量在FR计划下保持稳定，但在1年内逐渐增加。相比之下，二阶计划下的响应率低且随时间稳定。在FI 30分钟时间表下，FR组猴子的反应更高，反应模式并不表明FI表现，可能是由于实验历史。结论这些数据表明，在比例计划下可以观察到猴子可卡因摄入量的增加。使用FI 30分钟“探针”来评估“药物寻求”的变化似乎受到实验历史的影响。这些数据可能有助于可卡因滥用行为模型的发展，该模型侧重于吸毒的强迫性。
Rationale Studies in rodents have demonstrated that increased access to cocaine can result in increases in drug intake per unit time.Objectives The present studies characterized long-term changes in cocaine self-administration associated with quantitatively and qualitatively different conditions of cocaine availability in monkeys.Materials and methods Separate groups of rhesus monkeys (n=6/group) self-administered cocaine (0.2 mg/kg per injection) under a fixed ratio (FR) 30 schedule for 3 h twice daily for two consecutive days each week for 1 year, or responded under a second-order FR 10 (fixed interval 3-min:S) schedule of 0.2 mg/kg per injection cocaine during daily sessions. After 18 weeks, probe sessions were conducted once per week, in which responding was maintained under a fixed interval (FI) 30-min schedule in the presence of distinct stimuli.Results Weekly cocaine intakes under the FR schedule were stable in three subjects, but increased progressively in three monkeys over 1 year. In contrast, response rates under the second-order schedule were low and stable over time. Responding under the FI 30-min schedule was higher for monkeys in the FR group and pattern of responding was not indicative of FI performance, perhaps due to experimental history.Conclusions These data suggest that increases in cocaine intake can be observed under ratio schedules in monkeys. The use of an FI 30-min "probe" to assess changes in "drug seeking" appeared to be influenced by experimental history. These data may aid in the development of behavioral models of cocaine abuse, which focus on the compulsive nature of drug taking.