Pellis S M, McKenna M M
Department of Psychology, University of Lethbridge, Alta., Canada.
Behav Brain Res. 1992 Sep 28;50(1-2):135-45. doi: 10.1016/s0166-4328(05)80295-5.
Play fighting is a frequent activity of juvenile rats and appears to show marked variability amongst individuals in that some rats play a great deal and others very little. This study attempted to identify some of the factors involved in producing this individual variability. The major influence over an individual's frequency of play as a juvenile was found to be the frequency of play by the partner. That is, play appears to be contagious, in that a high playing animal stimulates its partner to play frequently as well. In male juveniles, but seemingly not in female juveniles, the subsequent adult status of one partner as dominant influences the subordinate-to-be to initiate more playful contacts. In addition to these extrinsic influences, however, there appear to be intrinsic factors that influence whether an individual is a high or low playing animal. One intrinsic factor appears to be 'boldness', so that bolder animals tend to initiate more playful contacts. Higher players tend to be more susceptible to the stereotypy-inducing effects of the dopamine agonist, apomorphine, and tend to be more dependent upon the playful activity of the partner to maintain their own high levels of play. Both of these characteristics are consistent with other studies comparing bold and timid rats. Boldness, however, only seems to influence how much play a rat will exhibit, not how much play it is capable of exhibiting. Neonatal testosterone augmentation increases juvenile play fighting but not apomorphine susceptibility, suggesting that a high player need not be a bold animal. The total frequency of play an individual is capable of initiating appears to depend upon perinatal exposure to androgens. Boldness and the playfulness of the partner appear to modulate the expression of this hormonally set value.
打闹玩耍是幼年大鼠常见的行为，而且个体之间差异明显，有些大鼠经常打闹，有些则很少。本研究试图找出导致这种个体差异的一些因素。研究发现，对个体幼年时玩耍频率影响最大的因素是同伴的玩耍频率。也就是说，玩耍似乎具有传染性，玩耍频繁的动物会刺激同伴也频繁玩耍。在雄性幼鼠中，但雌性幼鼠似乎并非如此，一个同伴随后成为占主导地位的成年个体，会促使未来的从属个体发起更多的玩耍互动。然而，除了这些外在影响因素外，似乎还有一些内在因素会影响个体是频繁玩耍还是很少玩耍。一个内在因素似乎是“大胆”，更大胆的动物往往会发起更多的玩耍互动。玩耍频繁的个体往往更容易受到多巴胺激动剂阿扑吗啡诱导刻板行为的影响，并且往往更依赖同伴的玩耍行为来维持自己的高玩耍水平。这两个特征与其他比较大胆和胆小大鼠的研究结果一致。然而，大胆似乎只影响大鼠表现出的玩耍量，而不影响其能够表现出的玩耍量。新生期睾酮水平升高会增加幼年大鼠的打闹玩耍，但不会增加对阿扑吗啡的易感性，这表明玩耍频繁的个体不一定是大胆的动物。个体能够发起的玩耍总频率似乎取决于围产期对雄激素的接触。大胆程度和同伴的玩耍倾向似乎会调节这种由激素设定的值的表达。
