The transition from a sexual to a parental brain via nest building

我们建议，筑巢，一种普遍的鸟类行为，提供了一个独特的窗口，了解物种如何从性过渡到父母的大脑。在大多数鸟类物种中，生殖的有性阶段的特征是性间和性内的行为相互作用，如领地，求偶和配偶守卫。其次是父母的行为，以确保生殖成功。一些支持性行为和生育的神经内分泌变化在鸟类中得到了很好的表征。然而，那些潜在的快速过渡，从一个性别的父母的大脑尚未被描述，提出了重要的基本问题，在这个关键的过渡期内和物种之间观察到的变化。鸟类的生殖活动是由下丘脑-垂体-性腺（HPG）轴组织的。这一精心调整的系统协调了中枢和外周激素的释放，使繁殖只有在环境条件足够好的时候才能成功地养育后代。为了响应HPG轴的刺激，性腺产生性类固醇激素，包括睾酮和17 β-雌二醇，这些激素起着调节生殖行为的中心作用。鸟类胚胎暴露于环境变化，如每日的温度波动或在发育过程中的捕食。为了减轻这些风险，大多数鸟类筑巢，它们的蛋被放置和孵化，和后代raised.We以前建立在斑胸草雀，Taeniopygia guttata，循环睾酮水平变化显着接近筑巢结束，这两个性类固醇敏感和不敏感的大脑区域在此行为期间活跃。在这里，我们建议建立性类固醇在大脑中的作用以及关键繁殖阶段过渡的分子和功能途径。结合尖端技术，我们将在求偶，筑巢和早期孵化期间在离散的大脑区域中观察性类固醇及其专用受体的局部变化，并将其与详细的行为分析相关联，以更好地了解这些行为/激素的关系（目标1）。我们还将确定性类固醇通过药理学操作影响这些行为的主要机制（目标2）。使用下一代测序和先进的生物信息学分析，我们将确定哪些基因在先前确定的已知为性类固醇敏感性位点的大脑区域中显示表达变化（目标3）。最后，在目标4中，我们将使用神经元追踪来研究在筑巢过程中强烈激活并且对性类固醇敏感的大脑区域和神经元网络（目标4）。因此，通过在快速行为转变期间对性类固醇及其在大脑中的受体的精细尺度变化进行第一次全面表征，再加上对它们所支持的分子和细胞网络的详细表征，我们将更好地了解大脑如何支持鸟类从有性生殖阶段过渡到亲代生殖阶段。

We propose that nest building, a widespread avian behaviour, offers a unique window to understand how species transition from a sexual to a parental brain. In most avian species, the sexual phase of reproduction is characterised by inter- and intra-sex behavioural interactions such as territoriality, courtship and mate guarding. This is followed by parental behaviours that ensure reproductive success. Some neuroendocrine changes that support sexual behaviour and parenthood are well characterised in birds. However, those underlying the rapid transition from a sexual to a parental brain are yet to be described, raising important fundamental questions regarding the variation observed both within and between species on this critical period of transition. Bird reproductive activities are organised by the hypothalamic-pituitary-gonadal (HPG) axis. This finely tuned system orchestrates central and peripheral hormone release enabling breeding to commence only when environmental conditions are good enough for successful offspring rearing. In response to HPG axis stimulation, the gonads produce sex-steroid hormones, including testosterone and 17B-oestradiol, that act centrally to regulate reproductive behaviour. Bird embryos are exposed to environmental changes, such as daily temperature fluctuations or predation during development. To mitigate these risks, most birds build nests into which their eggs are laid and incubated, and the offspring reared.We have previously established in zebra finches, Taeniopygia guttata, that circulating testosterone levels vary significantly towards the end of nest building, and that both sex-steroid sensitive and insensitive brain areas are active during this behaviour. Here we propose to establish where sex steroids act in the brain and the molecular and functional pathway(s) underlying key breeding stage transitions. Combining cutting-edge technologies, we will characterise the local variation(s) of sex steroids and their dedicated receptors in discrete brain areas during courtship, nest building and early incubation, and relate them to detailed behavioural analyses to better understand each of these behaviour/hormone relationships (Objective 1). We will also determine the main mechanisms through which sex steroids influence these behaviours using pharmacological manipulations (Objective 2). Using next generation sequencing and advanced bioinformatic analyses, we will determine which genes show expression changes in previously identified brain regions known to be sites of sex steroid sensitivity (Objective 3). Finally, in Objective 4 we will use neuronal tracing to characterise brain regions and neuronal networks that are strongly activated during nest building and are sex-steroid sensitive (Objective 4). Thus, by performing the first comprehensive characterisation of the fine-scale variations in sex steroids and their receptors in the brain during rapid behavioural transitions, coupled with a detailed characterisation of the molecular and cellular networks they support, we will better understand how the brain supports the transition from sexual to parental reproductive phase in birds.