Morphine-induced tolerance in the ileum and colon

吗啡和其他阿片类药物仍然是治疗中度至重度疼痛的最常用药物，包括癌症或手术引起的疼痛。本研究的总体目标是阐明吗啡和其他阿片类药物在回肠和大脑中诱导耐受的机制，而不是在结肠中导致便秘并限制这些优秀止痛药在人类中的长期使用。一位具有胃肠生理学方面的专门知识，另一位在研究吗啡和其他阿片类药物的急性和慢性作用方面具有丰富的经验，利用分子、细胞和整个动物方法。待检验的主要假设是结肠和回肠之间的细胞信号传导性质的差异导致回肠中而不是结肠中的吗啡诱导的耐受。我们进一步提出，在这些组织中，对各种阿片类药物的耐受性比率是相同的。我们的初步数据表明，作为显着的耐受性发展的抗伤害性吗啡的作用后，长期给药的小鼠，耐受性不发展其便秘的影响。第1年提出的工作的主要目标是阐明在体内和体外观察到的吗啡在不同组织中的耐受性差异是否与其他阿片类药物相同。在第二年，我们建议进一步评估我们有趣的发现，烟酰胺，一种内源性CD-38抑制剂，诱导结肠对吗啡的耐受性，这是一种以前没有报道过的现象。我们将检验以下假设：CD-38通路阻止结肠中的耐受性发展，并且在敲除动物中通过化学手段或遗传方式阻断CD-38通路允许耐受性发生。我们建议调查是否CD 38在其他组织，如回肠或脑引起的调节作用，在这些组织中的耐受性的发展以及。此外，我们将研究是否在信号转导过程中的其他步骤，如μ阿片受体的磷酸化，蛋白激酶C和A的活性，GRK改变阿片耐受性的发展类似或不同的各种组织。我们的初步数据表明，通过烟酰胺或8-溴环腺苷三磷酸核糖抑制CD 38通路导致结肠中对吗啡的耐受性的诱导。我们将测试烟酰胺，ryanodine和cADPribose对耐受性的发展和对吗啡的依赖性在分离的结肠肌条的影响，并确定是否抑制CD 38通路的结果在肠神经元中的μ受体磷酸化的变化。这项研究的长期主要公共卫生意义是使用这些信息来开发治疗慢性疼痛的药物，而不是便秘。这些研究还将增加我们对大脑中阿片类药物耐受性和最终身体依赖性发展的潜在机制的理解。

Morphine and other opioids remain the most frequently prescribed drugs for the treatment of moderate to severe pain, including pain due to cancer or surgery. The overall goal of this study is to elucidate the mechanisms of morphine and other opioid-induced tolerance in the ileum and brain but not in the colon which leads to constipation and limits the chronic use of these excellent pain relievers in man. This proposal represents a collaboration of two senior laboratories, one with expertise in gastrointestinal physiology and the other with extensive experience in studying the acute and chronic effects of morphine and other opioids, utilizing molecular, cellular and whole animal approaches. The main hypothesis to be tested is that differences in the cellular signaling properties between the colon and ileum result in morphine-induced tolerance in the ileum but not the colon. We further propose that the ratio of tolerance to various opioids is the same across these tissues. Our preliminary data demonstrate that as marked tolerance develops to the antinociceptive effects of morphine following chronic administration in mice, tolerance does not develop to its constipating effects. The major objective of the work proposed in year 1 is to elucidate whether this difference in tolerance in different tissues observed for morphine is the same for other opioids both in vivo and in vitro. In the second year we propose to further evaluate our interesting finding that nicotinamide, an endogenous CD-38 inhibitor, induces tolerance to morphine in the colon, a phenomenon not previously reported. We will test the hypothesis that the CD-38 pathway prevents tolerance development in the colon and that its blockade by either chemical means or genetically in knock out animals allows tolerance to occur. We propose to investigate whether CD38 in other tissues such as the ileum or brain causes a regulatory effect on the development of tolerance in these tissues as well. Further, we will investigate whether additional steps in the signal transduction process such as the phosphorylation of mu opioid receptors, the activity of protein kinase C and A, GRK alter opioid tolerance development similarly or differently in various tissues. Our preliminary data demonstrate that inhibition of the CD38 pathway by either nicotinamide or 8-bromo cyclic ADPribose results in the induction of tolerance to morphine in the colon. We will test the effects of nictoinamide, ryanodine and cADPribose on tolerance development and on dependence to morphine in the isolated colonic muscle strips and determine if inhibition of the CD38 pathways results in changes in mu receptor phosphorylation in enteric neurons. The long-term major public health implication of this research is the use of this information to develop medications to treat chronic pain that are devoid of constipation. These studies will also increase our understanding of the potential mechanisms in the development of tolerance and ultimately physical dependence to opioids in the brain.