The role of activity-dependent transcription in nicotine addiction-associated neuronal ensembles

烟草使用是导致死亡和疾病的主要可预防原因，全球每年有超过700万人死亡，仅在美国每年的直接医疗保健负担就达1700亿美元。尽管如此，尼古丁成瘾的神经机制仍知之甚少。许多大脑区域被尼古丁激活，但对细胞类型及其回路连接以及当它们在体内暴露于尼古丁时这些细胞和回路的变化知之甚少。记忆是由跨神经元集合体的独特活动模式编码的，这些神经元集合体的突触连接和兴奋性被经验改变，以促进或抑制它们在未来的重新激活。这种神经元集合的重新激活代表了长期记忆，无论是有意识的还是潜意识的，这些记忆塑造了我们的行为。我们希望在大脑皮层下奖赏回路中识别尼古丁敏感的集合体，并发现尼古丁暴露如何改变它们的突触连接和兴奋性。我们将尝试通过干扰细胞信号传导和基因转录因子来阻断尼古丁诱导的奖赏的形成，这些因子在这些细胞类型中被尼古丁激活，并介导大脑其他部位的细胞和行为适应。我们最近发表了迄今为止最广泛的研究，以确定尼古丁激活的神经元合奏免疫组织化学。从那时起，我们的实验室已经开发出分子工具来荧光标记体内尼古丁激活的神经元，使我们能够在活体脑切片或固定的组织块中直观地识别它们，不仅可以研究它们的细胞类型和大脑区域，还可以研究它们的电生理特性，突触连接和树突结构。我们的电生理分析揭示了这些细胞中的几种通道类型，这些通道类型已知控制兴奋性以及尼古丁激活的核钙信号和核钙激活的转录因子Npas4，Npas4已知对其他脑区域和环境中的突触连接和行为适应的修饰至关重要。需要进一步的工作来揭示这些细胞类型的神经递质，电路，通道特性和树突状结构，乳清是否被尼古丁修饰，以及这些修饰是否需要激活核钙和Npas4调节的基因表达。我们有工具来识别，分析和选择性地操纵这些细胞及其尼古丁反应，并评估尼古丁暴露的行为适应。通过这种方式，我们希望发现对尼古丁依赖发展至关重要的特定细胞类型中的功能机制和信号通路。这种方法可能会产生新的目标策略，以干扰尼古丁成瘾，以及确定在皮层下神经元合奏的长期变化的分子和细胞机制。

Tobacco use is the leading preventable cause of death and disease, with over 7 million deaths per year worldwide and an annual direct healthcare burden of $170 billion in the USA alone. Despite this, the neural mechanisms involved in nicotine addiction are poorly understood. Many brain regions are activated by nicotine, but little is known about the cell types and their circuit connections and what changes in these cells and circuits when they are exposed to nicotine in vivo. Memory is encoded by unique patterns of activity across neuronal ensembles whose synaptic connectivity and excitability are altered by experience to facilitate or repress their reactivation in the future. Such reactivation of a neuronal ensemble represents long-term memory, whether conscious or subliminal, and these memories shape our behavior. We wish to identify nicotine sensitive ensembles within the sub-cortical reward circuitry of the brain and discover how their synaptic connectivity and excitability are altered by nicotine exposure. We will attempt to block the formation of nicotine induced reward by interfering with cell signaling and gene transcription factors which are activated by nicotine in these cell types and which mediate cellular and behavioral adaptations elsewhere in the brain. We recently published the most extensive study to date to identify nicotine-activated neuronal ensembles using immunohistochemistry. Since then, our lab has developed molecular tools to fluorescently tag nicotine-activated neurons in vivo allowing us to visually identify them in live brain slices or fixed tissue blocks to investigate not only their cell type and brain region but also their electrophysiological properties, synaptic connectivity and dendritic structure. Our electrophysiological analysis has revealed several channel types in these cells which are known to control excitability as well nicotine-activated nuclear calcium signals and a nuclear calcium activated transcription factor, Npas4, which is known to be critical for modifications of synaptic connectivity and behavioral adaptations in other brain regions and contexts. Further work is required to reveal the neurotransmitters, circuits, channel properties and dendritic structure of these cell types, whether whey are modified by nicotine and whether these modifications require activation of nuclear calcium and Npas4 regulated gene expression. We have the tools to identify, analyze and selectively manipulate these cells and their nicotine responses and to assess the behavioral adaptations to nicotine exposure. In this way we hope to discover functional mechanisms and signaling pathways in specific cell types critical for the development of nicotine dependence. This approach may generate novel targets for strategies to interfere with nicotine addiction as well as identify the molecular and cellular mechanisms of long-term changes in sub-cortical neuronal ensembles.