Morphine administered shortly after exposure to a novel environment induces potent locomotor stimulant conditioning. Environmental novelty is important as pre-exposure (PE) to a stimulus can attenuate the capacity to acquire conditioned stimulus (CS). Here, the importance of environmental novelty for the efficacy of an open-field to become a CS for elicitation of a morphine conditioned response was assessed by comparing the effects of morphine administered post-trial following a 5 min exposure to a novel environment versus a PE environment. Four groups of rats (2 vehicle and 2 morphine groups) were used. Two groups received ten daily 5 min non-drug PEs to an open-field arena and the other two groups were not pre-exposed to the environment. Subsequently, all groups received post-trial injections of either vehicle or morphine immediately after each of five daily 5 min sessions in the open-field. Importantly, on the first day of testing prior to the first post-test morphine administration, the locomotor activity of the novel and PE groups was not different. Over the 5 post-trial morphine treatments, the activity of the PE morphine group, the PE vehicle and the novel environment vehicle groups did not change and were equivalent. In contrast, in the novel environment morphine group, a conditioned hyper-activity response increased with repeated post-trial morphine treatments. For the morphine group it is suggested that the novel environment initiated a post-trial stimulus trace that occurred in temporal contiguity with the post-trial drug response and enabled the trace to become a CS for the morphine unconditioned response. In contrast, PE induced a latent inhibition effect in the PE morphine group, thus the post-trial CS trace was insufficient to become associated to the morphine response and no conditioning occurred. In addition to conventional drug induced Pavlovian delay conditioning, the findings are suggestive of drug induced Pavlovian trace conditioning.

在暴露于新环境后不久服用的吗啡会引起有效的运动刺激条件。环境新颖性很重要，因为刺激的预暴露（PE）会削弱获得条件刺激（CS）的能力。在这里，通过比较暴露于新环境5分钟后在试验后施用吗啡的效果与PE相比，评估了环境新颖性对于开放视野成为CS诱发吗啡条件反应的功效的重要性。环境。使用四组大鼠（2个载体和2个吗啡组）。两组每天在露天场地上接受10次每天5分钟的非药物PE，其他两组未预先暴露于环境中。后来，在开阔地每天进行5次每天5分钟的训练后，所有组均立即接受媒介物或吗啡的试验后注射。重要的是，在首次服用吗啡后的测试的第一天，新的和PE组的运动活性没有差异。在5次吗啡治疗后的治疗中，PE吗啡组，PE媒介物和新型环境媒介物组的活性没有变化，并且是等效的。相比之下，在新型环境吗啡组中，条件性多动反应随着反复的试验性吗啡治疗而增加。对于吗啡组，建议该新环境启动了一个与试验后药物反应在时间上连续发生的试验后刺激痕迹，并使该痕迹成为吗啡无条件反应的CS。相反，PE在吗啡组中诱导了潜在的抑制作用，因此，试验后CS迹线不足以与吗啡反应相关，并且没有发生调节。除了常规药物诱导的巴甫洛夫延迟调理，该发现还暗示了药物诱导的巴甫洛夫痕量调理。