Distribution of Inhaled m-Xylene in Rat Brain and its Effect on GABA A Receptor Binding

Abstract: Distribution of Inhaled m-Xylene in Rat Brain and its Effect on GABA A Receptor Binding: Takehiko ITO, et al. Faculty of Education, Okayama University-Organic solvents generally depress the central nervous system (CNS), similarly to volatile anesthetics. The precise mechanism of their action on the CNS, however, is not fully understood, and remains to be clarified. This study is focused on how inhaled m-xylene distributes in the brain, and whether region specific change in GABA A receptor binding takes place due to the exposure. To conduct this study, we first developed a simple exposure system suitable for inhalation experiments with small animals. Using this system, six-week-old male Sprague-Dawley rats were exposed to m-xylene vapor (2000 ppm) 4 h/d, for 5 consecutive days. At the end of the exposure, m-xylene levels in four different regions of the brain were measured by head-space gas chromatography. Also 14 µm-thick frozen sections of the brain were made, and [ 35 S] t-butylbicyclophosphorothionate (TBPS) binding autoradiography was performed. Uneven distribution of m-xylene in the brain was observed. The concentration in the cerebellum (976 ± 93.4 µg/g tissue) was the highest, while that in the cerebral cortex (467 ± 43.6 µg/g tissue) was the lowest. Received June 29, 2001; Accepted Oct 13, 2001 Correspondence to: Takehiko Ito, Faculty of Education, Okayama University, 3-1-1 Tsushima-naka, Okayama City, 700-8530, Japan Despite the usefulness of organic solvents in industries, uncontrolled use of solvents may be hazardous to workers because of their acute and chronic toxicity 1) . Pharmacologically, organic solvents are generally central nervous system (CNS) depressants, and similar to volatile anesthetics. Because of their lipophilicity, they distribute in lipid-rich organs such as the brain, which is one of the main targets of the action of organic solvents. The neurotoxicity of organic solvents including xylene has been well documented In the present study we developed an exposure system suitable for inhalation experiments on small animals. With this system we exposed rats acutely to m-xylene, and examined the region specific distribution of inhaled m-xylene in the brain, as well as the distribution in other organs and tissues. In this way we have attempted to show whether m-xylene is evenly distributed in the brain or not. Because the functions of the brain are localized in discrete areas, the distribution of inhaled m-xylene in the brain was of particular interest. Several lines of evidenc

Complex chemistry of carbon nanotubes toward efficient and stable p-type doping

Abstract Developing efficient and stable carbon nanotube (CNT) doping techniques and elucidating their chemistry is essential for their further implementation in electronic and energy devices. Here, protonic acids and lithium salts are employed as p-type inducers and stabilizers of the doped state, respectively. Leveraging the electron-withdrawing capability of protons, protonic acids can easily induce heavily p-doped states in CNTs. Anionic species from the acids attach to the positively charged CNTs to achieve charge compensation. Introducing lithium salts with bulky, charge-delocalized anions to the p-doped CNTs results in an anion replacement driven by the free energy gain. The newly formed complexes demonstrate outstanding thermal stability in air, enduring a temperature of 100 °C for over a year. The chemical hardness of the applied anion effectively explains the difference in stability of the doped CNTs, indicating that the doping process and its stabilization can be understood and controlled through complex chemistry