Distribution of Exposed Organic Solvent in the Brain and its Effect on GABA_A Receptor

1.小动物接触有机溶剂新体系的建立建立了适用于大鼠接触间二甲苯的体系，并利用该体系进行了一系列实验。曝光系统很容易操作，而且很有用。用三种GABA_A受体特异性配体对间二甲苯暴露大鼠脑内GABA_A受体进行放射自显影研究。[^&lt；35&gt；S]硫代叔丁基二环磷酸盐的放射自显影显示小脑的结合显著增加，而使用[~3H]氟硝西潘的小脑结合无明显变化。为了进一步研究间二甲苯受体亚基特异性效应的可能性，用[~3H]Ro15-4513进行了放射自显影。大脑皮层II-III层、CA1、下丘和小脑颗粒细胞的结合有明显变化。颗粒细胞结合的增加似乎是一种亚基特异性的变化，可能是由于含有α6亚基的受体的改变。脑内多个区域间二甲苯浓度的测定暴露前后间二甲苯水平的测定，并以尿液中间二甲苯代谢物浓度作为参考。暴露时和暴露后尿间甲基马尿酸的测定。间二甲苯和间甲基马尿酸水平在暴露过程中呈平行变化，暴露后两种水平的下降幅度不同，为间二甲苯新的生物效应监测提供了基础数据。新的生物监测方法将以GABA_A受体的变化作为生物效应的指标，以尿间二甲苯的代谢物(间甲基马尿酸和/或其前体间甲苯醛)作为接触的指标。

1. Establishment of a new system for exposing organic solvents to small animalsA system suitable for exposing m-xylene to rats was made, and a series of experiments was conducted using this system. The exposure system was easy to handle, and was useful.2. Effects of m-xylene exposure on GABA_A receptor in the brainAutoradiographic study was done using three ligands specific to GABA_A receptors. Autoradiography using [^<35>S]t-butylbicyclophosphorothionate revealed a significant increase in the binding in the cerebellum, whereas that using [^3H]flunitrazepam showed no significant changes. To further investigate the possibility of a receptor subunit-specific effect of m-xylene, autoradiogram using [^3H]Ro15-4513 was obtained. Significant changes in binding were found in the II-IIIth layer of the cerebral cortex, CA1, Inferior colliculus and in the granule cells of the cerebellum. The increase in the binding in the granule cells seemed to be a subunit-specific change, possibly due to alteration in alpha6 subunit-containing receptors.3. Measurement of m-xylene concentration in several areas of the brainThe levels of m-xylene on and after the exposure were measured, and referenced with its metabolite concentration in urine.4. Measurement of m-methylhippuric acid in urine on and after the exposureThe levels of m-methylhippuric acid were measured on and after the exposure. While m-xylene level and m-methylhippuric acid level paralleled during the exposure, the two levels decreased in a different manner after the exposure.These findings taken together, the basic data to develop a new biological effect monitoring of m-xylene were obtained. The new biological monitoring method will use changes in GABA_A receptor as indices of biological effect, and metabolite of m-xylene in urine (m-methylhippuric acid and/or its precursor m-tolualdehyde) as indices of the exposure, respectively.