ADENOSINE RECEPTORS IN THE DIGESTIVE TRACT

这是一项研究腺苷受体的修订方案。 小肠。该项目旨在检验这一普遍假设 腺苷通过以下方式调节神经元活动和递质释放 与肌膜上不同种类的受体相互作用 可能与腺苷环化酶/cAMP系统偶联的神经元。这个 该项目将使用电生理和生化方法以及 肠源性突触体内腺苷能信息转导的研究 显微解剖肌间神经丛和酶分离神经节 准备工作。该项目旨在对受体亚型进行分类 它们调节AH/2型神经元和S/1型神经元的突触活动。 这些受体与腺苷环化酶的偶联将在 新型蛋白激酶A对cAMP依赖的调节作用研究 激动剂/拮抗剂对Sp-腺苷-3‘-5’-环单硫代硫酸酯 (CAMP)/RP-cAMP，百日咳毒素，特异性cAMP依赖 磷酸二酯酶抑制剂，环化酶抑制剂MDL 12,330A，垂体 腺苷环化酶激活多肽和cAMP的测定 分离的肌间神经节。肌醇磷脂/蛋白的作用 将用蛋白质研究腺苷能反应中的激酶C系统 激酶C激动剂和抑制物。的动作电位时程 AH/2型神经元将作为研究直接影响的模型系统 钙离子内流。只有AH/2型神经元具有胞体的假说 腺苷受体将在比较形态的研究中进行测试， 电生理和对腺苷的反应。内源性腺苷可能 对肌间神经元电活动施加紧张性抑制音 该受体可能与AH/2型神经元中的腺苷环化酶有关。 这一假设将通过干预措施进行检验，这些干预旨在阻止 内源性腺苷的作用。慢突触兴奋在AH/2型中的作用 神经元被认为是通过激活cAMP第二 信使系统。拟议的研究将描述腺苷的特征 参与抑制5-羟色胺介导的慢兴奋的受体 在AH/2型神经元中诱发的突触后电位(慢EPSP) 神经节间连接的局灶性刺激。内源性抑制 嘌呤能激动剂释放5-羟色胺的研究将在分离的神经节和 肠源性突触体。集成来自这些独特模型的数据 系统，将阐明腺苷在肌细胞中的信号机制 神经元。神经元缺氧的模型也将提供对 内源性腺苷抑制神经传递的机制 肠道的病理状态，如缺血和炎症。

This is a revised proposal for investigation of adenosine receptors in the small intestine. The project is intended to test the general hypothesis that adenosine modulates neuronal activity and transmitter release by interacting with a heterogeneous population of receptors on myenteric neurons that may be coupled to the adenylate cyclase/cAMP system. The project will use electrophysiological and biochemical methods as well as enteric synaptosomes to study the transduction of adenosinergic messages in microdissected myenteric plexus and enzymatically dissociated ganglion preparations. The project is designed to classify the receptor subtypes which modulate the synaptic activity of AH/type 2 and S/type 1 neurons. The coupling of these receptors to adenylate cyclase will be tested in cAMP-dependent modulation studies with the novel protein kinase A agonist/antagonist pair Sp-adenosine-3'-5'-cyclomonophosphothioate (cAMPs)/Rp-cAMPs, pertussis toxin, specific cAMP-dependent phosphodiesterase inhibitors, the cyclase inhibitor MDL 12,330A, pituitary adenylate cyclase-activating polypeptide and cAMP measurements in dissociated myenteric ganglia. The role of the phosphoinositide/protein kinase C system in adenosinergic responses will be studied with protein kinase C stimulators and inhibitors. The action potential duration in AH/type 2 neurons will serve as a model system to study direct effects on calcium influx. The hypothesis that only AH/type 2 neurons possess somal adenosine receptors will be tested in studies that compare the morphology, electrophysiology and responses to adenosine. Endogenous adenosine may exert a tonic inhibitory tone on activity of myenteric neurons and the receptors involved may be linked to adenylate cyclase in AH/type 2 neurons. This hypothesis will be tested with interventions intended to block the actions of endogenous adenosine. Slow synaptic excitation in AH/type 2 neurons is believed to occur through activation of the cAMP second messenger system. The proposed studies will characterize the adenosine receptors that are involved in suppression of 5-HT-mediated slow excitatory postsynaptic potentials (slow EPSPs), elicited in AH/type 2 neurons by focal stimulation of interganglionic connectives. Inhibition of endogenous 5-HT release by purinergic agonists will be studied in isolated ganglia and enteric synaptosomes. Integration of the data from these unique model systems, will clarify the signaling mechanisms for adenosine in myenteric neurons. A model of neuronal hypoxia will also provide insight into the mechanisms by which endogenous adenosine suppresses neurotransmission in pathologic states of the gut such as ischemia and inflammation.