Department of Psychology, University of New Mexico, Albuquerque, NM 87131, USA.
Behav Brain Res. 2011 Oct 31;224(2):318-25. doi: 10.1016/j.bbr.2011.06.010. Epub 2011 Jun 17.
Early life stimulation is known to produce long-lasting changes in the brain and behavior. One such early stimulation method is the neonatal novelty exposure procedure which allows the isolation of the novelty effect from several prominent confounding factors inherent to the neonatal handling procedure. In two previous studies, we found long-lasting novelty effects on different sets of functional measures without accompanying preferential maternal care, even when the observation was made immediately after the novelty manipulation, a time when such preferential care is most likely to be expressed. Here, within a single cohort of Long-Evans male rats, we demonstrate that novelty exposure leads to enhancements across several functional domains, including increased disinhibition to novelty, enhanced spatial and social memory, and reduced aggression, again without the accompaniment of preferential maternal care. These findings extend novelty exposure effects to aggression and replicate previously known novelty exposure effects on spatial and social memory with extension to new developmental stages. Most importantly, these findings do not support the hypothesis that preferential maternal care towards novelty-exposed pups mediates the observed novelty effects. We discuss the possibility that the effects of neonatal novelty exposure are mediated via repeated activation of the hypothalamic-pituitary-adrenal (HPA) axis that serves to inoculate pups for future exposures to novelty and novelty-induced HPA activation and that maternal influence is likely to be expressed via its modulatory role-the mother sets the individual-family specific behavioral and hormonal context to allow the same early life experience to have a family-specific effect.
早期生活刺激会导致大脑和行为产生持久的变化。一种这样的早期刺激方法是新生动物新奇暴露程序，它可以将新奇效应与新生动物处理程序固有的几种突出的混杂因素分离出来。在之前的两项研究中，我们发现了对不同功能测量的持久新奇效应，而没有伴随优先的母婴照顾，即使观察是在新奇操作后立即进行的，此时最有可能表达这种优先照顾。在这里，在一组长耳雄性大鼠中，我们证明了新奇暴露会导致多个功能领域的增强，包括对新奇的抑制作用增强、空间和社交记忆增强以及攻击性降低，同样没有伴随优先的母婴照顾。这些发现将新奇暴露效应扩展到了攻击性上，并复制了以前已知的新奇暴露对空间和社交记忆的影响，同时扩展到了新的发育阶段。最重要的是，这些发现并不支持母婴照顾对新奇暴露的幼崽的偏好会介导观察到的新奇效应的假设。我们讨论了这样一种可能性，即新生动物新奇暴露的影响是通过反复激活下丘脑-垂体-肾上腺（HPA）轴来介导的，这种轴的作用是为幼崽未来对新奇和新奇诱导的 HPA 激活做好准备，而母婴的影响可能通过其调节作用来表达——母亲为个体-家庭特定的行为和激素环境设定了特定的行为和激素环境，以使相同的早期生活经历产生特定家庭的影响。
