Potegal M, Huhman K, Moore T, Meyerhoff J
Department of Medical Neurosciences, Walter Reed Army Institute of Research, Washington, D.C. 20307-5100.
Behav Neural Biol. 1993 Sep;60(2):93-102. doi: 10.1016/0163-1047(93)90159-f.
When singly housed under laboratory conditions, male Syrian golden hamsters routinely attack novel conspecific intruders introduced into their home cages. As we report here, after being repeatedly defeated by a larger, more aggressive intruder, such normal territorial aggression on the part of the resident hamsters is replaced by defensive behavior and flight. We have found that such conditioned defeat (CD) can be reliably induced by a series of 5-min trials with an aggressive intruder whether these trials are spread over 4 days or are all given on the same day. A useful behavioral criterion for the appearance of CD during acquisition is the first occurrence of anticipatory flight (AF), i.e., the first time the resident flees from the next aggressive intruder before being attacked. CD shows generalization: Animals trained to the AF criterion (AF Group) subsequently show defensive behavior toward, and even flee from, intruders which show absolutely no sign of aggressiveness. Animals in the AF Group persisted in such defense behavior for two test sessions; animals given three additional defeat trials beyond the appearance of AF (AF + 3 Group) showed a greater magnitude and persistence of defense and flight. A comparison of CD-trained animals which met a non-aggressive intruder (NAI) every day for 5 days to similarly trained animals which met the intruder only on the fifth day after acquisition suggests that CD diminishes passively as a function of time and not as the consequence of repeated encounters with a nonaggressive stimulus animal. We also found that near ideal NAIs could be prepared by treating nonaggressive hamsters with high doses of diazepam: animals so treated locomote more or less continuously around the cage virtually ignoring the subject. An unexpected observation was that subjects in the AF Group tended to closely follow these diazepam-treated, rapidly locomoting NAIs around the cage. Following may be an example of the "risk assessment" activities directed toward a potential threat. The development of a rapid and reliable technique for inducing CD in hamsters sets the stage for further physiological and pharmacological work on this interesting phenomenon.
在实验室条件下单独饲养时，雄性叙利亚金仓鼠通常会攻击被放入其笼舍的陌生同种入侵者。正如我们在此报道的，在被一只体型更大、更具攻击性的入侵者反复击败后，这些常住仓鼠原本正常的领地攻击性会被防御行为和逃跑行为所取代。我们发现，通过与一只具有攻击性的入侵者进行一系列5分钟的试验，无论这些试验是分散在4天进行还是在同一天全部完成，都能可靠地诱发这种条件性失败（CD）。在习得过程中，CD出现的一个有用行为标准是首次出现预期性逃跑（AF），即常住仓鼠在被攻击之前首次逃离下一个具有攻击性的入侵者。CD具有泛化性：训练至达到AF标准的动物（AF组）随后会对完全没有攻击性迹象的入侵者表现出防御行为，甚至会逃离。AF组的动物在两个测试环节中都持续表现出这种防御行为；在出现AF后再进行三次失败试验的动物（AF + 3组）表现出更强且更持久的防御和逃跑行为。将每天与一只无攻击性入侵者（NAI）接触5天的CD训练动物与仅在习得后第5天才接触该入侵者的类似训练动物进行比较，结果表明CD会随着时间的推移而被动减弱，而非与无攻击性刺激动物的反复接触所致。我们还发现，通过给无攻击性的仓鼠注射高剂量地西泮，可以制备出近乎理想的NAI：经如此处理的动物会在笼舍中或多或少持续活动，几乎无视受试对象。一个意外的观察结果是，AF组的受试对象往往会在笼舍中紧紧跟随这些经地西泮处理、快速活动的NAI。跟随行为可能是针对潜在威胁的“风险评估”活动的一个例子。在仓鼠中诱导CD的快速且可靠技术的发展，为针对这一有趣现象开展进一步的生理学和药理学研究奠定了基础。
