Molecular Neuropsychiatry Research Branch, NIH/NIDA Intramural Research Program, 251 Bayview Boulevard, Baltimore, MD 21224, USA.
Brain Res. 2010 Mar 8;1318:1-10. doi: 10.1016/j.brainres.2009.12.083. Epub 2010 Jan 6.
Methamphetamine (METH) is a psychostimulant that can cause long-lasting neurodegenerative effects in humans and animals. These toxic effects appear to occur, in part, via activation of dopamine (DA) D1 receptors. This paper assessed the possibility that the DA D1 receptor antagonist, SCH23390, might inhibit METH-induced changes in the expression of several members of immediate early genes (IEGs) which are known to control more delayed expression of other genes. We found that injections of METH (4x10 mg/kg, given at 2 h intervals) caused significant increases in c-fos and fra-2 expression which lasted from 30 min to 4 h. Pre-treatment with SCH23390, given 30 min before each METH injection, completely blocked METH-induced expression of c-fos, but only partially inhibited fra-2 mRNA expression. These results were confirmed by Western blot analysis which showed METH-induced changes in c-Fos protein expression that were blocked by pretreatment with SCH23390. There were also delayed METH-induced DA D1 receptor-dependent effects on fosB mRNA expression. Even though fra-1 expression was not affected by pretreatment with METH alone, the repeated injections of SCH23390 caused substantial decreases in fra-1 mRNA expression in both the presence and absence of METH. The repeated injections of METH caused no changes in the mRNAs for c-jun, junB or junD. However, there were significant increases in the phosphorylation of c-Jun protein (ser63). Phosphorylation of c-Jun occurred in a delayed fashion (16 and 24 h after the last METH injections) and was attenuated by SCH23390 pretreatment. Interestingly, SCH23390 given alone caused significant decreases in phospho-c-Jun at all time-points. The METH injections also caused delayed induction in the expression of members of the Egr family of transcription factors in a DA D1 receptor-dependent fashion. Repeated injections of SCH23390 caused substantial suppression of basal striatal egr-1 and egr-2 mRNA expression but not of that of egr-3. Both crem and arc mRNA levels were induced by METH in a SCH23390-sensitive fashion. Moreover, multiple injections of SCH23390 given alone caused marked inhibition of basal arc expression. These results show that multiple injections of METH can differentially affect the expression of several IEGs, some of which occurred in a DA D1 receptor dependent fashion. The SCH23390-mediated suppression of basal fra-1, egr-1, and egr-2 mRNA levels suggests that their basal expression in the striatum might be dependent on tonic stimulation of the DA D1 receptor.
甲基苯丙胺（METH）是一种精神兴奋剂，可在人类和动物中引起持久的神经退行性作用。这些毒性作用似乎部分是通过激活多巴胺（DA）D1 受体发生的。本文评估了 DA D1 受体拮抗剂 SCH23390 是否可能抑制 METH 诱导的几种即刻早期基因（IEG）表达的变化，这些基因已知可控制其他基因的更延迟表达。我们发现，METH（4x10mg/kg，每 2 小时给予一次）注射可导致 c-fos 和 fra-2 表达显著增加，持续 30 分钟至 4 小时。SCH23390 在每次 METH 注射前 30 分钟预先给药可完全阻断 METH 诱导的 c-fos 表达，但仅部分抑制 fra-2mRNA 表达。Western blot 分析证实了这一点，该分析显示 METH 诱导的 c-Fos 蛋白表达变化被 SCH23390 预处理阻断。还存在迟发性 METH 诱导的 DA D1 受体依赖性 fosB mRNA 表达变化。尽管单独用 METH 预处理不会影响 fra-1 的表达，但重复注射 SCH23390 会导致 fra-1mRNA 在存在和不存在 METH 的情况下的表达大量减少。重复注射 METH 不会引起 c-jun、junB 或 junD 的 mRNA 变化。然而，c-Jun 蛋白（丝氨酸 63 位）的磷酸化显著增加。c-Jun 的磷酸化发生在延迟的时间（最后一次 METH 注射后 16 和 24 小时），并被 SCH23390 预处理减弱。有趣的是，SCH23390 单独给药会在所有时间点显着降低磷酸化 c-Jun。METH 注射还以 DA D1 受体依赖性方式诱导 Egr 家族转录因子成员的延迟表达。重复注射 SCH23390 会导致基础纹状体 egr-1 和 egr-2mRNA 表达的大量抑制，但不会导致 egr-3 的表达抑制。CREM 和 ARC mRNA 水平以 SCH23390 敏感的方式被 METH 诱导。此外，单独多次注射 SCH23390 会导致基础 ARC 表达的明显抑制。这些结果表明，多次注射 METH 可使几种 IEG 的表达产生差异，其中一些以 DA D1 受体依赖性方式发生。SCH23390 介导的基础 fra-1、egr-1 和 egr-2mRNA 水平的抑制表明它们在纹状体中的基础表达可能依赖于 DA D1 受体的紧张性刺激。
