INTERACTION BETWEEN NICOTINE AND STRESS

尼古丁和压力之间的相互作用

• 批准号: 3208880
• 负责人: BURT M SHARP
• 金额: $ 27.9万
• 依托单位: HENNEPIN HEALTHCARE RESEARCH INSTITUTE
• 依托单位国家: 美国
• 财政年份: 1985
• 资助国家: 美国
• 起止时间: 1985-03-31 至 1994-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3208880
• 关键词: adrenergic receptor; adrenocorticotropic hormone; autoradiography; brain mapping; brain metabolism; brain stem; colchicine; corticotropin releasing factor; dosage; drug administration rate /duration; electrochemistry; experimental brain lesion; gene expression; glucocorticoids; high performance liquid chromatography; hormone regulation /control mechanism; hypothalamus; in situ hybridization; laboratory rat; messenger RNA; neurochemistry; nicotine; nicotinic receptors; pharmacokinetics; physical chemical interaction; physiologic stressor; radioimmunoassay; radiotracer; serotonin; stress; tobacco abuse; transcription factor

Nicotine exerts both stimulant and depressant effects on the CNS which may modify its responses to stress. The ACTH axis has been used as a model to understand how nicotine acutely stimulates the rat brainstem-hypothalamic unit. Studies to further elucidate this stimulant effect of nicotine and its desensitization will focus on the neurochemical interaction between catecholamines originating in the brainstem, hypothalamic corticotropin releasing factor (CRF) and plasma ACTH. Investigations are also proposed to assess whether nicotine (i) affects brain function by altering genomic expression, and (ii) depresses neuronal genomic responses to non-nicotinic stimuli, such as CRF, which may be involved in coordinating CNS responses to stress. To localize and quantitate the depressive effects of nicotine, we plan to use the expression of c-fos mRNA, product of a rapid, early response gene, as an index of neuronal genomic responses to two stimuli: (i) metrazole, which as been shown to induce neuronal c-fos expression, and (ii) CRF, which we have shown induces c-fos. The neurochemical studies of nicotine stimulated ACTH secretion will correlate the turnover rates of hypothalamic CRF vs epinephrine and norepinephrine in rats pretreated with intracisternal colchicine or alpha-methyl-p-tyrosine, respectively, using HPLC with electrochemical detection of catecholamines. In these studies, a single dose of i.v. vs fourth ventricular (i.c.v.) nicotine will be compared. The effects of catecholamine depletion or adrenergic antagonists on CRF turnover and ACTH secretion in response to i.c.v. nicotine will be determine. Chronic, repetitive dosing with nicotine will also be studied to clarify the neurochemistry underlying desensitization of the ACTH response to nicotine. The effects of acute and chronic exposure to nicotine on the levels of hypothalamic CRF mRNA will be evaluated to determine whether chronic exposure causes neuronal adaptation. In many studies, the hypothalamic vs extra-hypothalamic effects of nicotine will be compared by in-situ hybridization or in tissue obtained by microdissection. Finally, the proximal site(s) mediating the effect of nicotine on ACTH secretion will be determine after local neurotoxic ablation or by infusing nicotine into selected brainstem cell groups. To determine whether chronic vs acute exposure to nicotine depresses the expression of c-fos mRNA in response to neuronal activation by metrazole or CRF, c-fos mRNA levels will be quantitated by dot-blot and Northern hybridization analysis of specific microdissected nuclei. The role of glucocorticoid feedback in mediating nicotine's affect on c-fos expression will be assessed in adrenalectomized vs glucocorticoid-replaced rats. Finally, intraparenchymal nicotine will be used to evaluate whether the depressive effect of nicotine is mediated locally. In summary, these studies test the hypothesis that a single exposure to nicotine stimulates the release of brain CRF, leading to ACTH secretion as part of a coordinated response similar to a stress response, whereas chronic exposure desensitizes CRF neurosecretory responses and depresses c-fos responses stimulated by CRF.

尼古丁对中枢神经系统既有兴奋作用又有抑制作用， 改变它对压力的反应。 ACTH轴已被用作模型， 了解尼古丁如何刺激大鼠脑干-下丘脑 单位 研究进一步阐明尼古丁的这种刺激作用， 它的脱敏作用将集中在神经化学的相互作用， 源于脑干的儿茶酚胺、下丘脑促肾上腺皮质激素 释放因子（CRF）和血浆ACTH。 还建议进行调查 为了评估尼古丁（i）是否通过改变基因组而影响脑功能， 表达，和（ii）抑制神经元基因组对非烟碱类的反应。 刺激，如CRF，可能参与协调CNS反应 压力 为了定位和定量尼古丁的抑郁作用， 我们计划使用c-fos mRNA的表达，这是快速、早期的产物， 反应基因，作为神经元基因组对两种刺激的反应的指标： (i)美曲唑，其已显示诱导神经元c-fos表达，和 (ii)CRF，我们已经证明诱导c-fos。 神经化学研究 尼古丁刺激的促肾上腺皮质激素分泌将与 预处理大鼠下丘脑CRF与肾上腺素和去甲肾上腺素 脑池内秋水仙碱或α-甲基-p-酪氨酸，分别使用 高效液相色谱电化学检测法测定儿茶酚胺。 在这些研究中， 单剂量i. v. vs第四脑室（i. c. v.）尼古丁将 比较了 儿茶酚胺耗尽或肾上腺素能拮抗剂的影响 对CRF周转和ACTH分泌的影响， 决定。 还将研究尼古丁的慢性重复给药 阐明ACTH脱敏的神经化学基础 尼古丁的反应 急性和慢性暴露于 将评价尼古丁对下丘脑CRF mRNA水平的影响， 确定慢性暴露是否会导致神经适应。 在许多 研究表明，尼古丁的下丘脑与下丘脑外效应将 通过原位杂交或在通过显微切割获得的组织中进行比较。 最后，近端部位介导尼古丁对ACTH的作用， 分泌将在局部神经毒性消融后或通过输注 尼古丁进入选定的脑干细胞群。 为了确定是否慢性 与急性尼古丁暴露相比， 对美曲唑或CRF引起的神经元激活的反应，c-fos mRNA水平将 通过特异性的斑点印迹和北方杂交分析进行定量 显微解剖的细胞核。 糖皮质激素反馈在介导 尼古丁对c-fos表达的影响将在肾上腺切除的 与糖皮质激素替代大鼠相比。 最后，脑实质内尼古丁将 用于评估尼古丁的抑郁作用是否是由 在附近 总之，这些研究验证了一个假设，即一个单一的 暴露于尼古丁刺激大脑CRF的释放，导致ACTH 分泌作为类似于应激反应的协调反应的一部分， 而慢性暴露使CRF神经分泌反应脱敏， 抑制CRF刺激的c-fos反应。