McGregor Iain S, Schrama Laurens, Ambermoon Polly, Dielenberg Robert A
Department of Psychology, University of Sydney, A19 Sydney, NSW, Australia.
Behav Brain Res. 2002 Feb 1;129(1-2):1-16. doi: 10.1016/s0166-4328(01)00324-2.
The behavioural responses to two commonly used 'predator odours' were assessed in male Wistar rats. Cat odour was presented to rats in the form of a piece of collar that had been worn by a domestic cat. Fox odour was presented in an equivalent piece of (unworn) collar that had been impregnated with 2,4,5 Trimethylthiazoline (TMT)-an extract of fox faeces. Other rats were exposed to collars containing Triethylamine (TEA), a putrid fishy smell, or formaldehyde, which has an acrid irritating smell. Experiment 1 showed that rats approached cat odour, TMT and TEA significantly less than they did an unworn collar. However, only cat odour increased retreat to the hide box, reduced locomotor activity and elicited 'head out' behaviour. When tested immediately after odour exposure, only cat odour exposed rats showed increased anxiety in the elevated plus maze and suppressed activity in a 90-min general activity test. When returned to the odour-paired environment 24 h later in the absence of test odours, only rats that had previously received cat odour showed evidence of conditioned fear. Experiment 2 showed that rats given the benzodiazepine drug midazolam (0.5 mg/kg) display increased approach and decreased defensiveness towards a cat odour impregnated collar. In contrast, midazolam accentuated the avoidance of TMT and formaldehyde containing collars. Experiment 3 showed that when cat odour was presented in a small, enclosed environment, rats display increased body immobility, decreased grooming and increased orientation towards the odour-exuding stimulus. These responses were not seen with TMT or TEA containing collars. Taken together, these results suggest that while cat odour strongly elicits specific defensive behaviours in rats, TMT has effects that are more characteristic of an aversive odour. We suggest that the results of some previous studies using TMT may need to be reassessed.
在雄性Wistar大鼠中评估了对两种常用“捕食者气味”的行为反应。猫的气味以一块家猫戴过的项圈的形式呈现给大鼠。狐狸的气味则以一块等效的（未戴过的）项圈呈现，该项圈已用2,4,5-三甲基噻唑啉（TMT）——狐狸粪便的提取物进行了浸渍。其他大鼠暴露于含有三乙胺（TEA）（一种腐臭的鱼腥味）或甲醛（一种刺鼻的刺激性气味）的项圈中。实验1表明，大鼠接近猫的气味、TMT和TEA的程度明显低于它们接近未戴过的项圈的程度。然而，只有猫的气味会增加退回隐藏箱的次数、降低运动活动并引发“探头”行为。在气味暴露后立即进行测试时，只有暴露于猫的气味的大鼠在高架十字迷宫中表现出焦虑增加，并且在90分钟的一般活动测试中活动受到抑制。当在没有测试气味的情况下24小时后回到与气味配对的环境中时，只有之前接触过猫的气味的大鼠表现出条件性恐惧的迹象。实验2表明，给予苯二氮䓬类药物咪达唑仑（0.5毫克/千克）的大鼠对浸渍有猫的气味的项圈表现出接近增加和防御性降低。相比之下，咪达唑仑加剧了对含有TMT和甲醛的项圈的回避。实验3表明，当在一个小的封闭环境中呈现猫的气味时，大鼠表现出身体不动增加、梳理行为减少以及对散发气味的刺激物的朝向增加。含有TMT或TEA的项圈未观察到这些反应。综上所述，这些结果表明，虽然猫的气味在大鼠中强烈引发特定的防御行为，但TMT的作用更具有厌恶气味的特征。我们建议，一些先前使用TMT的研究结果可能需要重新评估。
