Marusich Julie A, Branch Marc N, Dallery Jesse
University of Florida, FL, USA.
Exp Clin Psychopharmacol. 2008 Aug;16(4):282-92. doi: 10.1037/a0012874.
Repeated exposure to cocaine often leads to tolerance to effects on operant behavior, whereas sensitization often develops to effects on locomotor activity. The purpose of the present set of experiments was to examine if locomotor sensitization to cocaine would develop in the presence or absence of an operant contingency in rats. In Experiment 1, rats lever pressed on an FR schedule of reinforcement, and were administered chronic cocaine. Tolerance to effects of cocaine on lever pressing developed in most subjects. No subjects developed locomotor sensitization even when the operant contingency was removed. Experiment 2 examined effects of chronic cocaine administration in rats with no exposure to an operant contingency. Tolerance developed to locomotor effects of cocaine in some subjects, but none developed sensitization. In Experiment 3, rats were exposed to a shorter drug regimen, and given time off before a sensitization-test session. Some, but not all subjects showed locomotor sensitization during the test session. The present results, therefore, show that locomotor sensitization to cocaine is not an inevitable consequence of repeated exposure to the drug.
反复接触可卡因通常会导致对其对操作性行为影响的耐受性，而对运动活动的影响则常常会产生敏化作用。本系列实验的目的是研究在大鼠中，无论有无操作性条件，对可卡因的运动敏化是否会发生。在实验1中，大鼠按固定比率强化程序按压杠杆，并接受慢性可卡因给药。大多数实验对象对可卡因对杠杆按压的影响产生了耐受性。即使去除了操作性条件，也没有实验对象出现运动敏化。实验2研究了未接触操作性条件的大鼠长期给予可卡因的影响。一些实验对象对可卡因的运动影响产生了耐受性，但没有一个出现敏化。在实验3中，大鼠接受较短的药物疗程，并在敏化测试前有停药期。部分而非所有实验对象在测试期间表现出运动敏化。因此，目前的结果表明，对可卡因的运动敏化并非反复接触该药物的必然结果。
