Arakawa Hiroyuki
Department of Psychology Graduate School of Letters Nagoya University, Furo-cho Chikusa-ku, Nagoya 464-8601, Japan.
Dev Psychobiol. 2007 Jul;49(5):522-30. doi: 10.1002/dev.20243.
The ontogeny of exploratory behavior depending on the intensity of threat in a modified open-field was investigated in male rats aged 40, 65, and 130 days, by comparing with less threatening condition with no shock and more threatening condition where they were exposed to mild electric shock. The number of crossings in a dim peripheral alley was counted as the level of activity. The total duration of stay in the central area was measured as the level of exploration. The number of entries and stretch-attend postures into a bright center square were measured as active exploratory behavior and the risk assessment behavior, respectively. When exposed to mild shock prior to the test, 40-day-old rats decreased these exploratory behaviors, while 65- and 130-day-old rats increased active exploratory behavior (Experiment 1). A lower level of exploratory behavior following a mild shock was found in 65 and 130-day-old rats isolated during the juvenile stage, but not in rats isolated after puberty (Experiment 2). These findings suggest that the direction of changes in exploratory behavior of male rats following an increase in potential danger showed ontogenetic transition, which is mediated by social experiences as juveniles, but not as adults. This transition may be associated with the emergence of active exploratory behavior during the juvenile stage, which is activated by social interaction.
通过将无电击的低威胁条件与暴露于轻度电击的高威胁条件进行比较，研究了40日龄、65日龄和130日龄雄性大鼠在改良旷场中探索行为的个体发生与威胁强度的关系。昏暗外周通道中的穿越次数被计为活动水平。在中央区域停留的总时长被测量为探索水平。进入明亮中央方块的次数和伸展关注姿势分别被测量为主动探索行为和风险评估行为。在测试前暴露于轻度电击时，40日龄大鼠减少了这些探索行为，而65日龄和130日龄大鼠增加了主动探索行为（实验1）。在幼年阶段隔离的65日龄和130日龄大鼠在轻度电击后探索行为水平较低，但青春期后隔离的大鼠则没有（实验2）。这些发现表明，随着潜在危险增加，雄性大鼠探索行为变化的方向呈现个体发生转变，这种转变由幼年而非成年时的社会经历介导。这种转变可能与幼年阶段主动探索行为的出现有关，该行为由社会互动激活。
