Although some of the clinical manifestations of substance use disorders might be superficially similar, it is highly likely that different classes of abused drugs including opioids (heroin, morphine, and oxycodone, other opioids) and psychostimulants (cocaine and amphetamines) cause different neuroadaptations in various brain regions dependent in the distribution and concentration of their biochemical sites of actions. In fact, different molecular networks are indeed impacted by acute and chronic administration of addictive substances. Some of the genes whose expression is influenced by the administration of these substances are immediate-early genes (IEGs). IEGs include classes of low expression genes that can become very highly induced within seconds or minutes of activation by endogenous or exogenous stimuli. These IEGs might play important roles in activating target genes that regulate adaptations implicated in the behavioral manifestations diagnosed as addiction. Therefore, the purpose of this review is to provide an overview of recent data on the effects of psychostimulants and opioids on IEG expression in the brain. The review documents some contrasting effects of these classes of drugs on gene expression and indicates that further studies are necessary to identify the specific effects of each drug class when trying to predict clinical responses to therapeutic agents.

中文翻译：

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在大脑奖赏回路中立即早期基因的表达：精神刺激药和阿片类药物的差异调节。

尽管物质使用障碍的某些临床表现可能在表面上相似，但是很可能不同种类的滥用药物，包括阿片类药物（海洛因，吗啡和羟考酮，其他阿片类药物）和精神兴奋剂（可卡因和苯丙胺）在各种方面引起不同的神经适应性脑区取决于其生化作用部位的分布和浓度。实际上，不同的分子网络确实受到成瘾性物质的急性和慢性给药的影响。其表达受这些物质的施用影响的一些基因是立即早期基因（IEG）。IEG包括一类低表达基因，它们可以在被内源或外源刺激激活后的几秒钟或几分钟内被高度诱导。这些IEG在激活靶基因中可能起重要作用，该靶基因调节与被诊断为成瘾的行为表现有关的适应性。因此，本综述的目的是概述精神刺激药和阿片类药物对大脑中IEG表达的影响的最新数据。该综述记录了这些类别的药物对基因表达的一些对比作用，并指出，在试图预测对治疗药物的临床反应时，有必要进行进一步的研究以鉴定每种药物的特定作用。