Mechanisms of Ethanol's Reversal of Opioid Tolerance

描述（由申请人提供）：文献中有相当多的证据表明，由于同时滥用乙醇和阿片类药物（如海洛因或处方阿片类药物）导致的死亡在尸检时导致血液中阿片类药物的水平低于仅因阿片类药物死亡后观察到的水平。我们进行了一项广泛的研究，表明乙醇或地西泮的剂量不改变吗啡的急性作用，逆转了慢性吗啡产生的抗痛感耐受性。两种药物产生的逆转机制的不同之处是，单独使用GABAA或GABAB受体抑制剂并不能逆转酒精的作用，但阻断两种GABA受体可完全逆转乙醇对吗啡耐受性的影响。相反，地西泮对吗啡耐受的抑制作用被GABAA抑制剂完全逆转，而GABAA抑制剂则不能。本提案中所描述的工作的总体目标是阐明乙醇和其他影响中枢神经系统的药物联合施用逆转阿片类药物耐受性的细胞机制。利用转基因小鼠和一些分子技术，我们将进一步阐明GABA受体的作用和参与这些作用的信号机制。在第二个具体目标中，我们建议阐明乙醇和地西泮是否逆转对阿片类药物的耐受性，如丁丙诺啡和美沙酮，这些药物用于维持治疗，羟考酮和其他有滥用史的处方阿片类药物。我们和其他人已经报道了不同阿片类药物耐受性发展机制的差异。例如，蛋白激酶A和蛋白激酶C抑制剂而不是GIRK抑制剂逆转了对吗啡和其他中等效阿片类药物的耐受性，但对高效的DAMGO却没有。GIRK抑制剂对DAMGO有耐受性，但对其他阿片类药物没有。这些对阿片类药物耐受性发展机制的差异促使我们研究乙醇和/或地西泮是否会逆转对各种功效阿片类药物的耐受性。显然，如果阿片类药物受到乙醇或地西泮的不同影响，我们将阐明不同的机制。在第三个具体目标中，我们将研究乙醇和地西泮是否也能逆转对阿片类药物外周效应的耐受性。我们和其他人已经发现大脑和胃肠道中阿片类药物耐受机制之间存在某些差异，现在我们建议确定乙醇和/或地西泮是否能逆转胃肠道中的阿片类药物耐受。从这些实验中获得的信息将为我们和其他人继续阐明阿片类药物耐受性的机制提供重要信息。

DESCRIPTION (provided by applicant): There is considerable evidence in the literature that deaths due to the simultaneous abuse of ethanol with opioids such as heroin or prescription opioids leads to lower blood levels of the opioid upon autopsy than is observed following death due to the opioid alone. We have carried out an extensive study which has shown that either ethanol or diazepam at doses that do not alter the acute effects of morphine reversed the antinociceptive tolerance produced by chronic morphine. The mechanism of the reversal produced by the two drugs differed in that inhibitors of either GABAA or GABAB receptors alone did not reverse the effect of alcohol but blocking both type GABA receptors completely reversed the effect of ethanol on morphine tolerance. Conversely the inhibition of morphine tolerance produced by diazepam was completely reversed by a GABAA inhibitor alone but not by the GABAB inhibitor. The overall objective of the work described in this proposal is to elucidate the cellular mechanisms by which opioid tolerance is reversed by the concomitant administration of ethanol and other agents affecting the central nervous system. Using genetically altered mice and a number of molecular techniques we will elucidate further the role of GABA receptors and the signaling mechanisms involved in these effects. In the second specific aim we propose to elucidate whether ethanol and diazepam reverses the tolerance to opioids such as buprenorphine and methadone which are used in maintenance therapy and oxycodone and other prescription opioids with a history of abuse. We and others have reported differences in the mechanism of tolerance development for various opioids. For instance, protein kinase A and protein kinase C inhibitors but not GIRK inhibitors reversed tolerance to morphine and other moderately efficacious opioids but not to the high efficacy DAMGO. GIRK inhibitors revered the tolerance to DAMGO but not the other opioids. These differences in the mechanism of tolerance development to various opioids cause us to investigate whether ethanol and/or diazepam will reverse the tolerance to opioids of various efficacies. Obviously, we will elucidate the differing mechanisms if the opioids are affected differently by ethanol or diazepam. In the third specific aim we will investigate whether ethanol and diazepam also reverse tolerance to a peripheral effect of opioids. We and others have found certain differences between the mechanisms of opioid tolerance in the brain and the gastrointestinal tract and now we propose to determine whether ethanol and/or diazepam reverses opioid tolerance in the gastrointestinal tract. The information gained from these experiments will provide important information as we and others continue to elucidate the mechanism of opioid tolerance.