Geist T D, Ettenberg A
Department of Psychology, University of California, Santa Barbara 93106, USA.
Pharmacol Biochem Behav. 1997 May-Jun;57(1-2):145-50. doi: 10.1016/s0091-3057(96)00300-0.
Rats traversing a straight-alley for reinforcing stimuli typically exhibit faster running times as training proceeds. In previous work from this laboratory, animals running for a reinforcement consisting of intravenous infusions of cocaine, unexpectedly demonstrated a progressive increased time to enter the goalbox over trials. Closer observation revealed that the animals were exhibiting a unique retreat behavior (i.e., stopping their forward advance toward the goalbox and returning toward the startbox). It was hypothesized that the retreat behavior reflected an inherent conflict that originated from concurrent positive and negative associations with the goalbox. Such associations were attributed to cocaine's dual and well documented reinforcing and anxiogenic effects. To test this idea, the present study compared the runway behavior of animals that concurrently received food and mild foot shock in the goalbox to the behavior of the other animals running for cocaine. Results demonstrated that food + shock reinforced animals took longer to enter the goalbox and made more retreats than a control group that received only food in the goalbox. Both these effects were reversed by pretreatment with the anticonflict, anxiolytic drug, diazepam. The behavior pattern of animals that received the combination of food and footshock was found to strongly resemble that of IV cocaine-reinforced rats, a result consistent with the notion that chronic cocaine administration has both positive and negative consequences.
为了获取强化刺激而在直道上穿梭的大鼠，通常会随着训练的进行而表现出更快的奔跑速度。在本实验室之前的研究中，为了获得由静脉注射可卡因组成的强化物而奔跑的动物，在试验过程中进入目标箱的时间意外地逐渐增加。进一步观察发现，这些动物表现出一种独特的退缩行为（即停止向目标箱前进并返回起始箱）。据推测，这种退缩行为反映了一种内在冲突，这种冲突源于与目标箱同时存在的正向和负向关联。这种关联归因于可卡因众所周知的双重作用，即强化作用和致焦虑作用。为了验证这一想法，本研究将在目标箱中同时接受食物和轻度足部电击的动物的跑道行为与为了可卡因而奔跑的其他动物的行为进行了比较。结果表明，接受食物+电击强化的动物进入目标箱的时间更长，并且比仅在目标箱中接受食物的对照组做出更多的退缩行为。这两种效应都被抗冲突、抗焦虑药物地西泮预处理所逆转。发现接受食物和足部电击组合的动物的行为模式与静脉注射可卡因强化的大鼠的行为模式非常相似，这一结果与长期使用可卡因具有正负两方面后果的观点一致。
