Dissecting hormonal & neural control of social behavior in a transgenic cichlid

在整个动物界，领土和生殖行为通常是天生的，这表明它们的潜在神经基质是遗传的。在脊椎动物中，许多这些行为是由类固醇激素睾酮及其代谢产物控制的。发育中和成年大脑暴露于睾酮导致行为的男性化，并且在大多数物种的雄性中，睾酮（或代谢物）对于成年时引发交配和攻击行为是必要的。性腺类固醇如睾酮的产生由表达神经肽促性腺激素释放激素（GnRH1）的下丘脑神经元控制。这些神经元中的一些投射到脑垂体，在那里它们控制促性腺激素促黄体激素和促卵泡激素释放到血液中。这些激素结合睾丸中的受体，刺激睾丸激素的产生。GnRH1神经元的另一个子集投射到大脑的其他地方，但这些神经元的功能相关性尚未得到测试。GnRH1神经元表现出动态的细胞，电生理和基因转录相关的生殖和领土的行为，使他们的候选神经元，以调节行为输出。为了操纵GnRH1神经元，我将转基因修改慈鲷鱼，Astatotilapia burtoni，在这些细胞中特异性表达硝基还原酶，使其能够以时间控制的方式消融。在本研究中，利用这些鱼的实验将直接测试GnRH1神经元在转基因成体A. burtoni。此外，激素操纵的行为效应与GnRH1神经元消融的比较将揭示GnRH1神经元通过激素合成与产生这些行为的神经回路的直接连接对生殖和领土行为的相对贡献。这种转基因动物模型中，GnRH 1神经元可以有条件地消融成鱼将提供一个系统，以了解这些神经元如何有助于行为，并可能提供洞察他们的生育，青春期和更年期的调节。

Throughout the animal kindgdom, territorial and reproductive behaviors are often innate, indicating that their underlying neural substrates are genetically hardwired. Among vertebrates, many of these behaviors are controlled by the steroid hormone testosterone and its metabolites. Exposure of developing and adult brains to testosterone results in the masculinization of behavior, and in males of most species testosterone (or a metabolite) is necessary for the elicitation of mating and aggressive behavior as adults. The production of gonadal steroids such as testosterone is controlled by neurons of the hypothalamus expressing the neuropeptide gonadotropin releasing hormone (GnRH1). Some of these neurons project to the pituitary, where they control the release of the gonadotropins luteinizing hormone and follicle stimulating hormone into the bloodstream. These hormones bind receptors in the testes, stimulating the production of testosterone. Another subset of GnRH1 neurons project elsewhere in the brain, but the functional relevance of these neurons has not been tested. GnRH1 neurons exhibit dynamic cellular, electrophysiological, and gene transcription correlates of reproductive and territorial behaviors, making them candidate neurons to regulate behavioral outputs. To manipulate GnRH1 neurons, I will transgenically modify a cichlid fish, Astatotilapia burtoni, to express nitroreductase specifically in these cells, enabling their ablation in a temporally controlled manner. Experiments utilizing these fish in this proposal will directly test the function of GnRH1 neurons for behavior in transgenic adult A. burtoni. Further, comparison of the behavioral effects of hormone manipulation to GnRH1 neuron ablation will reveal the relative contributions of GnRH1 neurons to reproductive and territorial behavior via hormone synthesis versus direct connections to the neural circuits that generate these behaviors. This transgenic animal model in which GnRH1 neurons can be conditionally ablated in adult fish will provide a system to understand how these neurons contribute to behavior, and may provide insight into their regulation of fertility, puberty, and menopause.