Presynaptic modulation of anticholinesterase toxicity

描述（由申请人提供）：有机磷（OP）抗胆碱酯酶的毒性机制涉及一些可能被选择性影响的步骤，为差异毒性提供了基础。抑制毒蕈碱自身受体对乙酰胆碱的释放及其调控可能在OP毒性选择毒性中起关键作用。一些抗胆碱酯酶（包括对硫磷和毒死蜱的氧子，即对硫磷和毒死蜱氧子）直接与毒蕈碱M2受体（毒蕈碱自身受体的受体亚型）相互作用。利用脑切片测量乙酰胆碱的释放，我们注意到对磷和毒死蜱在体外作用的定性差异，以及体内暴露于对硫磷和毒死蜱后毒蕈碱自身受体功能改变的时间依赖性差异。假设毒蕈碱自身受体功能是胆碱能毒性的重要调节因子，其活性的选择性调节或与年龄相关的差异可导致不同的毒性。在目的1中，将在成年大鼠中使用微透析技术比较对硫磷和毒死蜱对体内胆碱能毒性和乙酰胆碱释放的剂量相关影响。老年大鼠对毒死蜱和对硫磷的急性作用更为敏感。aim 2的研究将评估乙酰胆碱释放/自身受体功能是否可能导致OP杀虫剂毒性的衰老相关差异。目的3将评估预先调节自身受体功能（通过输注自身受体激动剂、拮抗剂或M2受体反义剂）对成年大鼠对氧磷和毒死蜱氧磷毒性的影响。g蛋白受体激酶（GRK）依赖的M2受体磷酸化启动受体脱敏、内化和下调。Aim 4的研究将验证一些OP毒物会改变grk介导的M2受体磷酸化从而导致受体调控选择性改变的假设。这些研究将阐明OP杀虫剂对体内乙酰胆碱释放/自身受体功能的选择性作用，确定自身受体功能在年龄相关敏感性中的相对作用，并评估grk介导的M2调节通路的改变是否有助于某些OP毒物对毒蕈碱自身受体功能的选择性调节。

DESCRIPTION (provided by applicant): The mechanism of toxicity for organophosphorus (OP) anticholinesterases involves steps which may be selectively affected by some, providing a basis for differential toxicity. Acetylcholine release and its regulation by inhibitory muscarinic autoreceptors may be pivotally important in OP toxicant-selective toxicity. Some anticholinesterases (including the oxons of both parathion and chlorpyrifos, i.e., paraoxon and chlorpyrifos oxon) directly interact with muscarinic M2 receptors, the receptor subtype of muscarinic autoreceptors. Using superfused brain slices to measure acetylcholine release, both qualitative differences in the in vitro effects of paraoxon and chlorpyrifos oxon and time-dependent differences in the alteration of muscarinic autoreceptor function following in vivo parathion and chlorpyrifos exposures were noted. It is hypothesized that muscarinic autoreceptor function is an important modifier of cholinergic toxicity and that selective modulation or age-related differences in its activity can lead to differential toxicity. In aim 1, the dose-related effects of parathion and chlorpyrifos on cholinergic toxicity and acetylcholine release in vivo using microdialysis techniques will be compared in adult rats. Aged rats appear more sensitive to the acute effects of both chlorpyrifos and parathion. Studies in aim 2 will evaluate whether acetylcholine release/autoreceptor function may contribute to aging-related differences in OP insecticide toxicity. Aim 3 will evaluate the consequences of prior modulation of autoreceptor function (by infusion of autoreceptor agonist, antagonist or M2 receptor antisense) on paraoxon and chlorpyrifos oxon toxicity in adult rats. G-protein receptor kinase (GRK)-dependent phosphorylation of M2 receptors initiates receptor desensitization, internalization and down-regulation. Studies in Aim 4 will test the hypothesis that some OP toxicants differentially alter GRK-mediated phosphorylation of M2 receptors leading to selective changes in receptor regulation. These studies should clarify the selective effects of OP insecticides on acetylcholine release/autoreceptor function in vivo, determine the relative role of autoreceptor function in age-related sensitivity, and evaluate whether alteration of GRK-mediated M2 regulatory pathways contribute to the selective modulation of muscarinic autoreceptor function by some OP toxicants.