Biochemical and molecular research on NMDA and GABA ion-channel receptor complexes in animal model for schizophrenia

用体外定量受体放射自显影技术和原位杂交技术研究了间歇性腹腔注射可卡因（20 mg/kg）对[^ S] TBPS标记的印防己毒素位点<35>和GABA_A-BZD受体复合物α 1、α 6、β 2、γ 2亚基mRNA的影响。放射自显影采用荧光屏成像，灵敏度高，线性范围宽。结果表明，在3 nM [^<35>S] TBPS浓度下，大鼠17个脑区的[^S] TBPS结合率<35>均发生变化，在大脑皮质、海马结构、丘脑、腹侧苍白球、丘脑和小脑中均检测到各亚基mRNA的表达。刻板行为的平均得分随着注射次数的增加而增加。在<35>单次注射可卡因后24小时和长期给药14天的最后一次注射后1周，大鼠脑中任何区域的[^ S] TBPS结合均无显著变化。可卡因戒断大鼠在慢性给药1周后，<35>额叶皮质的II-III和IV层以及海马的CA 1区和齿状回的[^ S] TBPS结合显著增加。结果表明，GABA_A-BZD受体复合物各亚基mRNA在注射可卡因后1小时即发生明显变化，提示转录因子可能影响GABA_A-BZD受体复合物亚基mRNA的周转。此外，GABA_A-BZD受体复合物可能与可卡因戒断状态的形成密切相关，进一步研究GABA_A-BZD受体复合物中的其他结合位点对解释可卡因戒断状态和超敏反应的确切机制是必要的。

The effects of intermittent i.p. administration of cocaine (20 mg/kg) on the picrotoxin sites labeled by [^<35>S] TBPS and alpha1, alpha6, beta2, gamma2 subunit mRNA of GABA_A-BZD receptor complex were investigated by an in vitro quantitative receptor autoradiographic technique and in situ hybridization. Phosphor screen imaging with high sensitivity and wide linear range of response was utilized for autoradiography. Changes in [^<35>S] TBPS binding were examined in 17 brain regions at a concentration of [^<35>S] TBPS of 3nM.Each subunit mRNA was measured in the cerebral cortices, hippocampal formation, accumbens nucleus, ventral pallidum, thalamus and cerebellum.The behavioral changes induced by cocaine injection were manifested more rapidly. The mean scores of stereotyped behavior were increased with the number of injections. There was no significant change in [^<35>S] TBPS binding in the any regions in the brain of rats both 24 hr following a single injection of cocaine and 1 week after the final injection of chronic administrations for 14 days. The cocaine-withdrawal rats 1 week after chronic administration of cocaine showed a significant increase in [^<35>S] TBPS binding in the layr II-III and IV of frontal cortex, and the CA1 region and dentate gyrus of hippocampus. The significant change in each subunit mRNA was revealed only 1 hr after a single injection of cocaine.These findings suggest that the transcriptional factors might affect the turnover of subunit mRNA of GABA_A-BZD receptor complex. In addition, it raises the possibility that GABA_A-BZD receptor complex is closely involved in the development of cocaine withdrawal state.Further studies on the other binding sites in GABA_A-BZD receptor complex would be necessary for an explanation of precise mechanisms undelying the development of hypersensitization and cocaine-induced withdrawal state.