Phamracological and molecular biological analyzes on regulatory mechanisms for neurotransmitter receptor expression

通过测量[^3H] CGP-12177与小鼠大脑皮质神经元颗粒组分的结合以及暴露于β - ar拮抗剂纳多洛尔的神经元中β -1和β - ar的mrna，研究了神经递质受体，特别是β -肾上腺素能受体（β - ar）的外源性调节机制。纳多洛尔暴露后12小时内结合迅速增加，24小时后达到平台期。当测量[^3H] CGP-12177在每种β 2-和β 1- ar拮抗剂存在下的结合时，结合显著增加，表明对β 1-和β 2- ar的结合都增加了。Scatchard分析表明，这种结合的增加是由于Bmax值的增加，而Kd值没有变化。暴露24小时后，两种β - ar亚型的mRNA均显著增加，表明存在两种不同的加工过程，受体数量随mRNA的增加而增加，但未增加。暴露15分钟和1小时后，观察到zif286和c-fos mrna显著和短暂的增加。在暴露于纳多洛尔之前，zif286的反义诱导进入神经元可以消除纳多洛尔诱导的[^3H] CGP-12177结合的增加。这些结果表明，zif286的表达在β - ar的表达上调中起着重要作用。此外，还探讨了一氧化氮（NO）对GABA的释放机制。这两种材料都诱导GABA释放增加，这两种物质都依赖于Ca^<2+>，而不依赖于Ca^<2+>。后一种释放类型是Na^+依赖的GABA转运系统的反向过程。NO增加Ca^<2+>的内流是由l型和P/ q型电压依赖性Ca^<2+>通道激活引起的。

Regulatory mechanisms for exoression of neurotransmitter receptors, especially beta-adrenergic receptors ( beta-AR), were investigated by measuring [^3H] CGP-12177 binding to the particulate fraction from mouse cerebral cortical neurons and mRNAs of beta1-and beta2-AR in neurons exposed to nadolol, an antagonist of beta-AR.Nadolol exposure induced rapid increase in the binding within 12 hrs and the binding attained its plateau after 24 hrs of the exposure. When measuring [^3H] CGP-12177 binding in the presence of each antagonist for beta2-and beta1-AR,the bindings significantly increased, indicating that the bindings to both beta1-and beta2-AR increased. Scatchard analysis revealed that this increase in the binding was due to Bmax balue without any changes in Kd value. mRNAs for both beta-AR subtypes increased significantly 24 hrs after the exposure, suggesting two distinct processers, increasing processer of receptor number with and without increase in mRNA.After 15 min and 1 hr of the exposure significant and transient increases in zif286 and c-fos mRNAs were observed. Induction of antisense for zif286 into the neurons before the exposure to nadolol abolished nadolol-induced increase in [^3H] CGP-12177 binding. These results indicate that the expression of zif286 plays a significant role in the expression of beta-AR upregulation. Inaddition, released of GABA release mechanisms by nitric oxide (NO) were investigated. Both materials induced increases in GABA release both dependent on Ca^<2+> and independent of Ca^<2+>. The latter type of release was the reverse process of Na^+-dependent GABA transport system. The increased influx Ca^<2+> of by NO is clarified to be caused by activation of L-and P/Q-typed voltage-dependent Ca^<2+> channels.