Cellular Mechanisms of Opioid Tolerance

阿片类药物是治疗疼痛最有效的药物。不幸的是，随着重复给药，它们的功效会下降 因为宽容的发展。这项研究的长期目标是了解 潜在的神经耐受机制，因此可以开发更有效的疼痛治疗方法。许多先前 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种不同的耐受机制， 不可能所有这些假定的机制都直接参与。拟议的研究将侧重于 腹外侧导水管周围灰质（PAG），试图确定耐受的因果机制。PAG神经元 特别适合于研究阿片类药物耐受性，因为将吗啡微量注射到PAG中会产生 抗伤害感受和重复显微注射产生耐受性。此外，神经元回路和细胞内 已经描述了阿片样物质通过其产生抗伤害感受的信号级联。拟议的研究将采取 细胞内和行为的耐受性措施的优势，试图了解神经化学 这些神经元的耐受性基础。耐受性可能是由信号通路沿着任何地方的变化引起的 从阿片受体到反馈回路本项目的目标将检查沿着这条道路的所有步骤沿着。目的 1将确定有助于阿片耐受的特定PAG神经元。目的2将决定受体是否 内化有助于宽容的发展。目标3将确定细胞内分子， 发展宽容。目标4将确定是否需要向PAG提供反馈， 宽容的发展。该项目的一个独特之处是，整个细胞记录将用于连接神经元 改变行为耐受性的测量方法。例如，细胞内信号级联被认为有助于 将系统地破坏耐受性，以确定该信号级联中的每个步骤对 阿片类药物耐受性的测量行为。体内和体外技术的组合使用提供了强有力的 了解分子变化和行为后果之间联系的方法。从长远来看，这样的 知识将有助于开发通过防止对疼痛的耐受来改善疼痛治疗的疗法。 阿片类药物

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.