Won J S, Song D K, Huh S O, Kim Y H, Suh H W
Department of Pharmacology and Institute of Natural Medicine, College of Medicine, Hallym University, Republic of Korea.
Hippocampus. 2000;10(3):236-43. doi: 10.1002/1098-1063(2000)10:3<236::AID-HIPO4>3.0.CO;2-B.
The in vivo short-term effect of melatonin on kainic acid (KA)-induced proenkephalin (proENK) or prodynorphin (proDYN) mRNA, and on AP-1 protein levels in the rat hippocampus, were studied. Melatonin (5 mg/kg) or saline was administered intraperitoneally (i.p.) to rats 30 min prior to and immediately after i.p. injection of KA (10 mg/kg). Rats were sacrificed 1 and 3 h after KA injection. The proENK and proDYN mRNA levels were significantly increased 3 h after KA administration. The elevations of both proENK and proDYN mRNA levels induced by KA were significantly inhibited by the preadministration with melatonin. The increases of proENK and proDYN mRNA levels induced by KA were well-correlated with the increases of c-Fos, Fra-2, FosB, c-Jun, and JunB protein levels, which were significantly increased 3 h after KA administration and effectively inhibited by administration with melatonin. In an electrophoretic mobility shift assay, both AP-1 and ENKCRE-2 DNA binding activities were increased by KA, which were also attenuated by the administration of melatonin. In addition, cross-competition studies revealed that AP-1 or ENKCRE-2 DNA binding activity was effectively reduced by the 50x unlabeled cross-competitor. Therefore, these data suggest that melatonin has an inhibitory role in KA-induced gene expression, such as proENK and proDYN mRNA expression, and this may be due to a reduction of KA-induced AP-1 or ENKCRE-2 DNA binding activity.
研究了褪黑素对大鼠海马体中 kainic 酸（KA）诱导的前脑啡肽原（proENK）或前强啡肽原（proDYN）mRNA 以及 AP-1 蛋白水平的体内短期影响。在腹腔注射 KA（10 mg/kg）前 30 分钟及注射后立即给大鼠腹腔注射褪黑素（5 mg/kg）或生理盐水。在 KA 注射后 1 小时和 3 小时处死大鼠。KA 给药后 3 小时，proENK 和 proDYN mRNA 水平显著升高。预先给予褪黑素可显著抑制 KA 诱导的 proENK 和 proDYN mRNA 水平升高。KA 诱导的 proENK 和 proDYN mRNA 水平升高与 c-Fos、Fra-2、FosB、c-Jun 和 JunB 蛋白水平升高密切相关，这些蛋白水平在 KA 给药后 3 小时显著升高，并通过给予褪黑素有效抑制。在电泳迁移率变动分析中，KA 增加了 AP-1 和 ENKCRE-2 DNA 结合活性，给予褪黑素也可使其减弱。此外，交叉竞争研究表明，50 倍未标记的交叉竞争剂可有效降低 AP-1 或 ENKCRE-2 DNA 结合活性。因此，这些数据表明褪黑素对 KA 诱导的基因表达具有抑制作用，如 proENK 和 proDYN mRNA 表达，这可能是由于 KA 诱导的 AP-1 或 ENKCRE-2 DNA 结合活性降低所致。
