Cellular adaptation to opiates alters ion-channel mRNA levels.

The chronic use of several drugs, including opiates, results in the stereotypical behaviors characteristic of addiction. Alterations in gene expression have been associated with the use of these addictive drugs. Previous studies, however, have been limited to describing changes in amounts of individual mRNAs from single tissue samples. Cellular adaptation to opiates, reflected in the regulation of the expression of many different mRNAs, seems likely to contribute to the complicated behaviors of addiction. The present studies examined coordinate alterations in the amounts of multiple mRNAs in the rat striatum and in NG108-15 cells after opioid stimulation or the precipitated withdrawal of opioid use. The experimental approach combined amplification of the poly(A)+ RNA population with reverse Northern blot analysis to simultaneously characterize the relative changes in several mRNAs. Morphine treatment of rats for 5 days was associated with a reduction in the amount of striatal RNA for the voltage-sensitive K+ channel without significant changes in other ion channels. In NG108-15 cells stimulation with the delta-opiate receptor agonist [D-Ala2,D-Leu5]enkephalin (DADLE) alone and followed by naloxone (precipitated withdrawal) caused relative changes in the abundances of several mRNAs. The composite effects of alterations in the abundance of multiple mRNAs (and the proteins they encode) in response to opioid use likely contribute to the development and maintenance of opiate-mediated behaviors. IMAGES:

包括阿片类药物在内的多种药物长期使用，会引发成瘾所特有的刻板行为。基因表达的改变与这类成瘾性药物的使用密切相关。然而此前的相关研究仅局限于描述单一样本组织中单个信使RNA（messenger RNA, mRNA）的含量变化。由多种不同mRNA的表达调控所体现的细胞对阿片类药物的适应性，或许正是促成成瘾复杂行为的关键因素。本研究针对阿片类药物刺激或阿片使用后的催促戒断（precipitated withdrawal），检测了大鼠纹状体与NG108-15细胞中多种mRNA含量的协同改变情况。本实验方法将聚腺苷酸尾RNA（poly(A)+ RNA）群体的扩增与反Northern印迹（reverse Northern blot）分析相结合，可同时表征多种mRNA的相对含量变化。对大鼠连续5天给予吗啡处理后，其纹状体中编码电压敏感钾通道的RNA含量出现下降，而其他离子通道的RNA含量无显著变化。在NG108-15细胞中，单独使用δ阿片受体激动剂[D-Ala²,D-Leu⁵]脑啡肽（DADLE），以及随后给予纳洛酮引发催促戒断，均会导致多种mRNA的丰度发生相对变化。阿片类药物使用引发的多种mRNA（及其编码的蛋白质）丰度改变所产生的综合效应，或许正是阿片介导行为的形成与维持的重要诱因。图像：