Mechanisms of Ethanol's Reversal of Opioid Tolerance

描述(申请人提供)：文献中有相当多的证据表明，与阿片类药物如海洛因或处方阿片类药物同时滥用导致的死亡在尸检时导致阿片类药物的血液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，表明无论是乙醇还是安定，在不改变吗啡急性效应的剂量下，都能逆转慢性吗啡产生的抗伤害耐受性。这两种药物的逆转机制不同，GABAA或GABAB受体的单独抑制剂不能逆转酒精的作用，但阻断这两种类型的GABA受体则完全逆转乙醇对吗啡耐受的影响。相反，地西潘对吗啡耐受性的抑制可被GABAA抑制剂完全逆转，但不能被GABAB抑制剂逆转。这项建议中描述的工作的总体目标是阐明阿片类药物耐受性被同时给予乙醇和其他影响中枢神经系统的药物逆转的细胞机制。利用转基因小鼠和一些分子技术，我们将进一步阐明GABA受体的作用和涉及这些效应的信号机制。在第二个具体目标中，我们建议阐明乙醇和安定是否逆转了对阿片类药物如丁丙诺啡和美沙酮的耐受性，这些阿片类药物用于维持治疗和羟考酮以及其他有滥用历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形成机制的差异。例如，蛋白激酶A和蛋白激酶C抑制剂但不能逆转对吗啡和其他中等有效阿片类药物的耐受性，但不能逆转高效阿片类药物DAMGO的耐受。GIRK抑制剂尊重对DAMGO的耐受性，但不是其他阿片类药物。这些不同的阿片类药物耐受形成机制的差异促使我们研究乙醇和/或安定是否会逆转不同疗效的阿片类药物的耐受。显然，如果阿片类药物受到乙醇或安定的不同影响，我们将阐明不同的机制。在第三个具体目标中，我们将研究乙醇和安定是否也逆转了对阿片类药物外围效应的耐受性。我们和其他人发现了大脑和胃肠道阿片类药物耐受机制的某些差异，现在我们建议确定乙醇和/或安定是否逆转胃肠道阿片类药物耐受。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.