Sculpting brain circuits with early experience

现在有压倒性的证据表明，新生儿的大脑处于非常可塑性的状态，因此即使是相对无害的干预措施也可能对成年人的生理产生长期影响。在我们之前的NSERC支持的研究计划中，我们研究了实验性新生儿热性惊厥导致大脑兴奋性长期变化的长期影响。我们了解到，仅由外周注射热原脂多糖(LPS)引起的炎症，引起的变化与热性惊厥引起的变化相似。这可能是因为包括促炎细胞因子和前列腺素在内的许多促炎分子在大脑中产生，并调节一些信号分子的活动，如内源性大麻素。促炎分子，如细胞因子和前列腺素，以及内源性大麻素，在未成熟大脑的正常发育过程中发挥作用。在生命早期，促炎分子和相关分子的过度信号很可能会干扰正常的发育过程。为了确定这些分子在新生儿期的过度信号是否会影响发育，我正在寻求资金，以发现新生儿炎症后中枢神经系统(CNS)功能和行为长期改变的潜在证据和机制。我将把重点放在一个重要的脑核--杏仁核上，在那里我们有成年人行为和电生理变化的初步证据。我的总体假设是：新生儿炎症会在成年后产生细胞因子介导的、长期的分子、电生理和行为变化。我研究计划的长期目标是更好地了解新生儿应激源如何影响大脑。我的具体短期目标集中在描述新生儿炎症信号的增加如何影响成人的杏仁核功能：1.确定杏仁核的突触和神经元膜属性是否因新生儿炎症而改变？新生的两性小鼠都会被注射脂多糖来诱导炎症。这些受试者的杏仁核脑片将在60天时收集，并将评估固有的兴奋性、突触前和突触后的特性以及内源性大麻素信号。2.确定新生儿炎症是否会改变杏仁核依赖行为。厌恶学习被认为是杏仁核功能的可靠测试；因此，与生理盐水处理的动物相比，在新生儿时期发炎的小鼠将受到限制，成年后学习行为的获得和灭绝将受到恐惧。确定导致成人行为和电生理改变的关键炎症变化？为了确定长期变化的原因机制，我们将确定炎症后新生儿杏仁核中哪些细胞被激活，哪些分子被释放。为了确定其中哪些是导致长期变化的原因，我将在炎症后的新生儿身上使用药理学试剂进行干预，或利用转基因动物来验证药理学，并确定炎症引起的电生理和行为变化在成年后是否会逆转。我们将通过使用受控良好的新生小鼠炎症模型以及实验室建立的体内行为、体外电生理和分子方法的组合来探索这些问题。

There is now overwhelming evidence that the neonatal brain is in a very plastic state, whereby even relatively innocuous interventions can have long-lasting effects upon adult physiology. In our previous NSERC supported research program, we studied the long-term effects of experimental neonatal febrile convulsions to cause long lasting changes in excitability of the brain. We learned that inflammation alone, caused by peripheral administration of the pyrogen, lipopolysaccharide (LPS), caused similar changes to those resulting from the febrile convulsion. This may be because a number of pro-inflammatory molecules including pro-inflammatory cytokines and prostaglandins are generated in the brain and regulate the activity of a number of signaling molecules such as endocannabinoids. Pro-inflammatory molecules such as cytokines and prostaglandins, as well as endocannabinoids, play a role in the normal developmental processes in the immature brain. It is likely that excess signalling by pro-inflammatory and related molecules in early life has the potential to interfere with normal developmental processes. To determine if excess signaling by these molecules during the neonatal period affects development, I am seeking funding to discover underlying evidence for, and mechanisms for long term altered central nervous system (CNS) function and behavior after neonatal inflammation. I will focus upon an important brain nucleus, the amygdala, where we have preliminary evidence for both behavioral and electrophysiological changes in adults. My overall hypothesis is that: Neonatal inflammation produces cytokine-mediated, long-term molecular, electrophysiological and behavioral changes in adults.The long term objectives of my research program are to better understand how neonatal stressors affect the brain. My specific short term objectives focus upon delineating how increased inflammatory signaling in the neonate affects amygdala function in the adult:1. Determine if synaptic and neuronal membrane properties in the amygdala are altered by neonatal inflammation? Neonatal mice of both sexes will be given lipopolysaccharide to induce inflammation. Brain slices of the amygdala will be collected from these subjects at 60 days age and intrinsic excitability, pre- and postsynaptic properties and endocannabinoid signaling will be assessed. 2. Determine if neonatal inflammation alters amygdala-dependent behaviors. Aversive learning is thought to be a reliable test for amygdala function; thus mice that were inflamed as neonates will be subjected, as adults to fear conditioning and acquisition and extinction of learned behavior compares with saline treated animals.3. Determine the key inflammatory changes that precipitate the altered adult behavior and electrophysiological changes? To determine causal mechanisms underlying long-term changes we will determine which cells are activated and which molecules are released in the neonatal amygdala after inflammation. To determine which of these are causal for the long-term changes, I will intervene with pharmacological agents, or make use of genetically modified animals to validate the pharmacology, in the neonate after inflammation and determine if the electrophysiological and behavioral alterations caused by inflammation are reversed in the adult.We will pursue these questions by using well-controlled neonatal mouse inflammatory models and a combination of in vivo behavioral, in vitro electrophysiological and molecular approaches that are well established in the lab.