DISSERTATION RESEARCH: Neuroendocrine Mechanisms Underlying Rapid Change in Social Behavior

社会行为快速变化背后的神经内分泌机制(0206677)首席研究员：约翰·罗伯特·戈德温博士生：凯瑟琳·安妮·塞姆萨环境和内部生理影响都会影响包括人类在内的动物的性行为和攻击性行为的表达。对于生活在不可预测的环境中的物种来说，展示性行为和/或攻击性行为的适当性可能会很快发生变化。许多研究都集中在对物理环境变化的适应上，但社会环境也可能同样不可预测，因此动物在面对社会变化时能够迅速适应它们的行为也是很重要的。在过去的二十年里，大量的工作已经证明了神经肽激素在调节从交配和父母照顾到配偶守卫和领土防御的社会行为中的重要作用。有两种神经肽激素起着特别重要的作用，它们是非哺乳动物中的精氨酸加压素(AVT)和哺乳动物中发现的非常相似的精氨酸加压素(AVP)。这些荷尔蒙在大脑中释放，并在已知与社会行为相关的区域改变神经功能。虽然许多研究表明这些激素对实验室行为的影响，但在完全复杂的自然环境中，研究AVT或AVP影响性行为和攻击行为的详细机制的研究仍然相对较少。这项研究将探索AVT影响性行为和攻击性行为的机制，以及决定这种激素对这些行为影响的性质的社会和荷尔蒙条件。实验模型是蓝头鱼，一种被广泛研究的改变性别和角色的珊瑚礁鱼。蓝头鲸表现出受社会控制的雌性到雄性的性别变化，在这种变化中，雌性可以在大约10天内成为具有功能的雄性。对于所提出的研究类型，该模式物种具有两个主要优势。首先，性别变化过程依赖于来自社会环境的线索，这使得它成为了解社会对神经功能的影响以及环境和内部激素线索在控制行为方面的相互作用的一个非常好的系统。其次，由于蓝头鲸在受保护的浅水水域有大量种群，而且非常容易捕获以进行标记和实验操作，因此可以在自然界中研究神经肽作用的机制。约翰·戈德温之前的研究表明，当雌性开始表现出男性行为时，下丘脑中AVT的表达会增加，在性别变化期间，她们的卵巢会变成睾丸。Katharine Semsar和John Godwin的研究表明，AVT可以在不占据领地的体型较大的雄性中诱导领土攻击和求爱行为，而AVT受体阻滞剂可以减少持有领地的雄性的这些行为。这项提案中概述的研究将确定：i)AVT是否对女性的行为转变为男性是必要的，以及增强AVT是否可以加速这一过程；ii)通过这种激素的受体衡量，对AVT的反应能力是否在性别变化过程中发生变化；以及iii)在性别变化过程中上升的一种有效的雄激素(11-酮睾丸酮)对AVT及其受体在大脑中的表达有何影响。这项工作应该会提高我们对行为适应和神经肽激素在这些过程中的作用的理解。这些机制具有很强的基础性意义，但也更为重要，因为攻击性行为会带来社会成本。

Neuroendocrine mechanisms underlying rapid change in social behavior (0206677)Principal Investigator: John Robert GodwinDoctoral Student: Katharine Anne SemsarBoth environmental and internal physiological influences affect the expression of sexual and aggressive behavior by animals including humans. For species that live in unpredictable environments, the appropriateness of displaying sexual and/or aggressive behavior can change quickly. A good deal of research has focused on adaptations to changes in the physical environment, but social environments can be equally unpredictable and it is therefore important that animals be able to adapt their behavior quickly in the face of social change as well. A large body of work over the past twenty years has documented important roles for neuropeptide hormones in mediating social behaviors ranging from mating and parental care to mate guarding and territorial defense. Two neuropeptide hormones found to play especially prominent roles are arginine vasotocin (AVT) in non-mammalian vertebrates and the very similar arginine vasopressin found in mammals (AVP). These hormones are released in the brain and act to alter neural function in areas known to be associated with social behavior. While many studies have shown effects of these hormones on behavior in the laboratory, there are still relatively few studies that have examined the detailed mechanisms by which AVT or AVP affect sexual and aggressive behavior in the full complexity of the natural environment. This study would explore mechanisms by which AVT affects sexual and aggressive behavior and the social and hormonal conditions that determine the nature of the effects of this hormone on these behaviors. The experimental model is the bluehead wrasse (Thalassoma bifasciatum), a well studied sex- and role-changing coral reef fish. Bluehead wrasses exhibit socially controlled female-to-male sex change in which females can become functional males within approximately ten days of becoming socially dominant. This model species has two principal advantages for the type of study proposed. First, the dependence of the sex change process on cues from the social environment makes it a very good system for understanding social influences on neural function and the interaction of environmental and internal hormonal cues in controlling behavior. Second, because of large populations in shallow, protected waters and extraordinary ease of capture for marking and experimental manipulations, bluehead wrasses allow the mechanisms underlying neuropeptide actions to be studied in nature. Previous work by John Godwin has shown that AVT expression increases in the hypothalamus as females begin to exhibit male behavior and their ovaries become testis during sex change. Studies by Katharine Semsar and John Godwin have shown that AVT can induce territorial aggression and courtship behavior in large males who do not hold territories while an AVT receptor blocker can reduce these behaviors in territory-holding males. The studies outlined in this proposal would determine: i) whether AVT is necessary for females to become males behaviorally and whether augmenting AVT can accelerate this process, ii) whether the ability to respond to AVT, as measured by receptors for this hormone, changes during sex change, and iii) what the effects of a potent androgenic hormone that rises during sex change (11-ketotestosterone) are on the expression of AVT and its receptor in the brain. This work should improve our understanding of behavioral adaptation and the role of neuropeptide hormones in these processes. These mechanisms are of strong basic interest, but also important more generally because of the societal costs of aggressive behavior.