Lauterborn Julie C, Truong Giang S, Baudry Michel, Bi Xiaoning, Lynch Gary, Gall Christine M
Department of Anatomy and Neurobiology, Gillespie Neuroscience Research Facility, University of California, Irvine, CA 92697-4292, UA.
J Pharmacol Exp Ther. 2003 Oct;307(1):297-305. doi: 10.1124/jpet.103.053694. Epub 2003 Jul 31.
The ampakine CX614 positively modulates alpha-amino-3-hydroxy-5methyl-4-isoxazolepropionic acid (AMPA) receptor-gated currents and increases brain-derived neurotrophic factor (BDNF) expression. In rat hippocampal slice cultures, CX614 rapidly increases BDNF gene expression but with time, mRNA levels fall despite the continued presence of active drug. The present study examined this apparent refractory period and the possibility that spaced ampakine treatments could sustain elevated BDNF protein levels. In cultured hippocampal slices, CX614, a second ampakine CX546, and the cholinergic agonist carbachol each increased BDNF mRNA levels with acute (3-h) treatment. After 4-day pretreatment with CX614, fresh ampakine (CX614 or CX546) did not induce BDNF mRNA, whereas carbachol did. Western blots confirmed that after an extended period of ampakine treatment, AMPA receptor protein levels are indeed reduced, suggesting that with longer treatments receptor down-regulation mediates ampakine insensitivity. Finally, using a "24-h on/24-h off" CX614 treatment protocol, the ampakine refractory state was circumvented, BDNF mRNA was induced with each ampakine application, and elevated BDNF protein levels were maintained through 5 days in vitro. These results suggest that spaced ampakine treatments can be used to sustain elevated neurotrophin levels and to test the utility of this manipulation for neuroprotection by endogenous neurotrophins.
安帕金CX614能正向调节α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）受体门控电流，并增加脑源性神经营养因子（BDNF）的表达。在大鼠海马切片培养物中，CX614能迅速增加BDNF基因表达，但随着时间推移，尽管活性药物持续存在，mRNA水平仍会下降。本研究探讨了这种明显的不应期，以及间隔使用安帕金治疗能否维持BDNF蛋白水平升高的可能性。在培养的海马切片中，CX614、另一种安帕金CX546以及胆碱能激动剂卡巴胆碱在急性（3小时）处理时均能增加BDNF mRNA水平。在用CX614进行4天预处理后，新鲜的安帕金（CX614或CX546）不能诱导BDNF mRNA，而卡巴胆碱则可以。蛋白质免疫印迹法证实，在长时间使用安帕金治疗后，AMPA受体蛋白水平确实降低，这表明随着治疗时间延长，受体下调介导了对安帕金的不敏感。最后，采用“24小时开启/24小时关闭”的CX614治疗方案，规避了安帕金不应期状态，每次使用安帕金均能诱导BDNF mRNA，并且在体外培养5天内维持了BDNF蛋白水平升高。这些结果表明，间隔使用安帕金治疗可用于维持神经营养因子水平升高，并测试这种操作对内源性神经营养因子神经保护作用的效用。
