REGULATION OF ALPHA-2 ADRENERGIC RECEPTORS

去甲肾上腺素和肾上腺素是脑内重要的神经递质， 中枢神经系统和α-2肾上腺素能受体， 结合腺苷酸环化酶的抑制作用，分布广泛。 临床上，α-2肾上腺素能激动剂如可乐定和胍那苄 用于治疗高血压以及其他几种疾病。 而 可乐定被认为是控制血压的中枢药物， 其作用机制尚不清楚。 的疗效 α-2肾上腺素能激动剂通常仅在慢性 治疗，表明适应性变化的参与。 因此 更好地了解的调节和作用机制， α-2肾上腺素能受体，它们与α-2肾上腺素能受体的偶联及其调节 腺苷酸环化酶，具有明显的发展潜力， 药物治疗 拟议研究的总体目标是 了解孵化效应的分子基础， 用α-2肾上腺素能激动剂预孵育细胞， α-2肾上腺素能受体结合和酶的活性 腺苷酸环化酶 有三种效应需要研究。 一是 受体数量的下调和环磷酸腺苷的脱敏 AMP反应。 第二种是刺激性cAMP的增敏作用 在与α-2激动剂预孵育后产生。 出现了 是两种类型的致敏作用，它们可能具有不同的机制。 第三个作用是增强毛喉素刺激的环磷酸腺苷 通过与（高浓度） α-2激动剂 我们建议确定这些影响的机制 在三个细胞系中，每个细胞系表达三种假定的 α-2肾上腺素能受体亚型，然后确定是否有任何 差异是细胞类型特异性的或受体亚型特异性的（或 也许是两者的组合）。 我们的总体方法是首先研究 这些现象在正常情况下 表达每种α-2肾上腺素能受体亚型，然后研究 稳定转染的细胞系（通常缺乏受体） 分别与每一个亚型。

Norepinephrine and epinephrine are important neurotransmitters in the central nervous system, and alpha-2 adrenergic receptors, which are coupled to the inhibition of adenylate cyclase, are widely distributed. Clinicallly, alpha-2 adrenergic agonists such as clonidine and guanabenz are used to treat hypertension as well as several other disorders. While clonidine is thought to act centrally to control blood pressure, its mechanism of action is not well understood. The therapeutic effects of alpha-2 adrenergic agonists often are ivident only after chronic treatment, suggesting the involvement of adaptive changes. Thus, a better understanding of the regulation and the mechanism of action of alpha-2 adrenergic receptors, their coupling to and their regulation of adenylate cyclase, has a clear potential for the development of better drug therapies. The overall goal of the proposed research is to understand the molecular basis for the effects of incubation and preincubation of cells with an alpha-2 adrenergic agonist on subsequent alpha-2 adrenergic receptor binding and the activity of the enzyme adenylate cyclase. There are three effects to be studied. The first is the down-regulation of receptor number and desensitization of the cyclic AMP response. The second is the sensitization of stimulated cyclic AMP production following preincubation with an alpha-2 agonist. There appear to be two types of sensitization, which may have different mechanisms. The third effect is the potentiation of forskolin-stimulated cyclic AMP production by concurrent incubation with (a high concentration of) an alpha-2 agonist. We propose to determine the mechanisms of these effects in three cell lines, each of which express one of the three putative alpha-2 adrenergic receptor subtypes, and then determine if any differences are cell type specific or receptor subtype specific (or perhaps a combination of both). Our overall approach is to first study the mechanism of these phenomena in the three cell lines which normally express each alpha-2 adrenergic receptor subtype, and then to study a cell line (which normally lacks the receptor) stably transfected separately with each of the subtypes.