Cellular Mechanisms of Opioid Tolerance

描述（由申请人提供）：阿片类药物是治疗疼痛最有效的药物。不幸的是，由于耐受性的发展，它们的疗效随着反复给药而下降。这项研究的长期目标是了解耐受性的潜在神经机制，从而开发出更有效的疼痛治疗方法。许多先前的研究已经检查了阿片类药物耐受性。然而，这些研究显示了超过30种不同的耐受性机制，不太可能所有这些假定的机制都直接参与。拟议的研究将集中在腹外侧导水管周围灰质（PAG）的耐受性上，试图确定耐受性的因果机制。PAG神经元特别适合研究阿片类药物耐受性，因为在PAG中微量注射吗啡会产生抗痛觉，反复微量注射会产生耐受性。此外，神经元回路和细胞内信号级联通过阿片类药物产生抗感觉已被描述。拟议的研究将利用细胞内和行为的耐受性测量，试图了解这些神经元耐受性的神经化学基础。耐受性可能是由从阿片受体到反馈回路的信号通路的任何地方的变化引起的。这个项目的目的是研究这条道路上的所有步骤。目的1将确定促进阿片耐受性的特定PAG神经元。目的2将确定受体内化是否有助于耐受性的发展。目的3将确定有助于耐受性发展的细胞内分子。Aim 4将确定对PAG的反馈是否对耐受性的发展是必要的。这个项目的一个独特之处在于，整个细胞的记录将被用来将神经元的变化与耐受性的行为指标联系起来。例如，被认为有助于耐受性的细胞内信号级联将被系统地破坏，以确定该信号级联中每个步骤对行为测量的阿片类药物耐受性的贡献。体内和体外技术的结合使用为理解分子变化和行为后果之间的联系提供了有力的方法。从长远来看，这些知识将有助于通过防止对阿片类药物的耐受性来改善疼痛治疗的疗法的发展。

DESCRIPTION (provided by applicant): Opioids are the most effective treatment for pain. Unfortunately, their efficacy decreases with repeated administration because of the development of tolerance. The broad long-term objective of this research is to understand the underlying neural mechanisms for tolerance so more effective pain treatments can be developed. Many previous studies have examined opioid tolerance. However, these studies show over 30 different mechanisms for tolerance, and it is unlikely that all of these putative mechanisms are directly involved. The proposed studies will focus on tolerance in the ventrolateral periaqueductal gray (PAG) in an attempt to identify causal mechanisms for tolerance. PAG neurons are particularly well suited for studying opioid tolerance because microinjection of morphine into the PAG produces antinociception and repeated microinjections produce tolerance. In addition, the neuronal circuitry and intracellular signaling cascades through which opioids produce antinociception have been described. The proposed studies will take advantage of both intracellular and behavioral measures of tolerance in an attempt to understand the neurochemical basis of tolerance in these neurons. Tolerance could be caused by a change anywhere along the signaling pathway from opioid receptors to feedback circuits. The aims of this project will examine all of the steps along this pathway. Aim 1 will identify the specific PAG neurons that contribute to opioid tolerance. Aim 2 will determine whether receptor internalization contributes to the development of tolerance. Aim 3 will identify the intracellular molecules that contribute to the development of tolerance. And Aim 4 will determine whether feedback to the PAG is necessary for the development of tolerance. A unique feature of this project is that whole cell recordings will be used to link neuronal changes to behavioral measures of tolerance. For example, the intracellular signaling cascades believed to contribute to tolerance will be systematically disrupted to determine the contribution of each step in this signaling cascade to opioid tolerance measured behaviorally. The combined use of in vivo and in vitro techniques provides a powerful approach to understanding the link between molecular changes and behavioral consequences. In the long term, such knowledge will contribute to the development of therapies that improve pain treatment by preventing tolerance to opioids.