SELECTIVITY OF MUSCARINIC DRUGS IN BRAIN

这项研究检验了毒碱胆碱能 结合标准和第二信使确定的受体亚型 老鼠大脑中的系统。为了实现这一目标，有限数量的 毒扁豆碱类配体，是根据表观 将筛选第二信使系统的选择性 高密度脂蛋白受体区域分布的放射自显影研究 配基的亲和力。最具选择性的配体--既有激动剂，也有 拮抗者--将被检查其刺激/对抗能力 M受体介导的磷脂酰肌醇代谢的刺激 腺苷环化酶抑制和GTP酶刺激的比较 不同的大脑区域。海马体、脑干和小脑 被选为三个典型的大脑区域，似乎拥有 受体亚型的群体相对一致但不同。我们的 初步数据表明，不同激动剂的区域特异性 可能与他们刺激特定秒数的能力无关 信使系统。区域选择性配基的筛选 受体放射自显影是通过比较 各种配体竞争通用拮抗剂(~3H) 苯甲酸喹烷基酯(~3H)-QNB。该方法的优点是 在同一个化验中可以直接比较配基的数量。其影响 检查了第二信使系统上的配体的数量，比较了与 不同的结合选择性。肌醇磷酸盐在治疗后的累积 选择了(~3H)肌醇预标记法和c-AMP的蓄积法 因为它们代表了两条主要的受体刺激的代谢途径 导致细胞反应。受体刺激的GTP水解酶 代表着接近受体占有率的一步，涉及毒鼠强 受体介导的腺苷环化酶抑制，最可能是在 还可刺激磷脂酰肌醇(PI)的代谢。如果这些研究 按预期进行，我们将第一次能够清楚地显示 基于结合的区域选择性独立于 对大脑中第二信使系统的选择性。这 信息应有助于认知和其他方面的合理药物设计 由于中枢胆碱能功能受损而导致的缺陷。

The research examines the relationship between muscarinic cholinergic receptor subtypes as identified by binding criteria and second messenger systems in the rat brain. To accomplish this goal a limited number of muscarinic ligands, which have been selected on the basis of apparent selectivities for second messenger systems will be screened autoradiographically for the regional distribution of receptors having high affinities for the ligands. The most selective ligands--both agonists and antagonists--will be examined for their abilities to stimulate/antagonize muscarinic receptor-mediated stimulation of phosphatidylinositol turnover, inhibition of adenylate cyclase and stimulation of GTPase, comparing different brain areas. The hippocampus, brainstem and cerebellum have been selected as three prototypical brain areas that appear to possess relatively uniform but disparate populations of the receptor subtypes. Our preliminary data suggest that regional specificities of various agonists may not be related to their abilities to stimulate a particular second messenger system. Screening of ligands for regional selectivity by receptor autoradiography is performed indirectly by comparing the abilities of various ligands to compete for the universal antagonist (3H) quineclidinyl benzilate (3H)-QNB. The method has the advantage that a number of ligands can be compared directly in the same assay. The effects of ligands on second messenger systems are examined, comparing areas with different binding selectivities. Accumulation of inositol phosphates after prelabeling with (3H) inositol and accumulation of c-AMP have been selected because they represent the two major receptor-stimulated metabolic pathways leading to cellular responses. Receptor-stimulated GTP hydrolysis represents a step close to receptor occupancy involved in the muscarinic receptor-mediated inhibition of adenylate cyclase and most probably in the stimulation of phosphatidyl inositol (PI) turnover also. If the studies proceed as expected, we will be able to show clearly for the first time that regional selectivity based on binding is independent of the selectivity for the second messenger systems in the brain. This information should aid in rational drug design for cognitive and other deficits that result from the impairment of central cholinergic function.