Siviy Stephen M, Eck Samantha R, McDowell Lana S, Soroka Jennifer
Department of Psychology, Gettysburg College, Gettysburg, PA 17325, USA.
Department of Psychology, Gettysburg College, Gettysburg, PA 17325, USA.
Physiol Behav. 2017 Feb 1;169:147-154. doi: 10.1016/j.physbeh.2016.11.035. Epub 2016 Dec 5.
A cross-fostering design was used to assess the relative involvement of genetic variability and early postnatal experiences on differential levels of playfulness in juvenile Fischer 344 (F344) and Lewis (LEW) rats and the extent to which strain differences in anxiety may influence play in these two strains. F344 dams were found to lick and groom their pups less than LEW dams and this was not dependent upon the strain of the pups in the litter. As expected, F344 rats were less playful than LEW rats as demonstrated by fewer playful contacts directed to the nape of a Sprague-Dawley (SD) partner and a decreased likelihood of rotating completely to a supine position when their nape was contacted by the SD partner. These differences could not be readily explained by parallel strain differences in anxiety. The pattern of effects on play as a function of cross-fostering depended on both the genetic background of the pup and the motivational state of the pup prior to testing. Whereas in-fostered LEW pups solicited more play as isolation prior to testing increased from 4 to 24h, cross-fostered pups of both strains as well as in-fostered F344 pups were relatively insensitive to the motivational modulation of play solicitation. Responsiveness to play solicitations in pups of both strains reared by F344 dams was insensitive to prior isolation whereas pups reared by LEW dams were less likely to respond with a complete rotation to a supine position when solicited as isolation increased from 4 to 24h prior to testing. These data suggest that the overall level of playfulness in a particular strain of rat is fairly resistant to cross-fostering and may be particularly sensitive to genetic variation whereas how this urge is titrated and modified by motivational factors may be influenced more by epigenetic factors.
采用交叉抚育设计来评估遗传变异性和出生后早期经历对幼年费希尔344（F344）和刘易斯（LEW）大鼠玩耍水平差异的相对影响，以及焦虑方面的品系差异可能在多大程度上影响这两个品系的玩耍行为。研究发现，F344母鼠舔舐和梳理幼崽的次数少于LEW母鼠，且这并不取决于一窝幼崽的品系。正如预期的那样，F344大鼠比LEW大鼠更少玩耍，表现为与斯普拉格-道利（SD）伙伴颈部的玩耍接触较少，且当SD伙伴接触其颈部时，完全翻转至仰卧姿势的可能性降低。这些差异无法通过焦虑方面的平行品系差异轻易解释。作为交叉抚育函数的玩耍效应模式取决于幼崽的遗传背景和测试前幼崽的动机状态。虽然饲养在本窝的LEW幼崽在测试前的隔离时间从4小时增加到24小时时会寻求更多玩耍，但两个品系的交叉抚育幼崽以及饲养在本窝的F344幼崽对玩耍寻求的动机调节相对不敏感。由F344母鼠饲养的两个品系幼崽对玩耍寻求的反应对先前的隔离不敏感，而由LEW母鼠饲养的幼崽在测试前隔离时间从4小时增加到24小时时，被寻求玩耍时完全翻转至仰卧姿势的可能性较小。这些数据表明，特定品系大鼠的总体玩耍水平对交叉抚育具有相当的抗性，可能对遗传变异特别敏感，而这种冲动如何被动机因素调节和改变可能更多地受表观遗传因素影响。
