Katsura M, Higo A, Tarumi C, Tsujimura A, Takesue M, Mohri Y, Shuto K, Ohkuma S
Department of Pharmacology, Kawasaki Medical School, 701-0192, Kurashiki, Japan.
Brain Res Mol Brain Res. 2000 Sep 15;80(2):132-41. doi: 10.1016/s0169-328x(00)00119-4.
We investigated the mechanisms underlying the increase in diazepam binding inhibitor (DBI) and its mRNA expression induced by nicotine (0.1 microM) exposure for 24 h using mouse cerebral cortical neurons in primary culture. Nicotine-induced (0.1 microM) increases in DBI mRNA expression were abolished by hexamethonium, a nicotinic acetylcholine (nACh) receptor antagonist. Agents that stabilize the neuronal membrane, including tetrodotoxin (TTX), procainamide (a Na(+) channel inhibitor), and local anesthetics (dibucaine and lidocaine), dose-dependently inhibited the increased expression of DBI mRNA by nicotine. The nicotine-induced increase in DBI mRNA expression was inhibited by L-type voltage-dependent Ca(2+) channel (VDCC) inhibitors such as verapamil, calmodulin antagonist (W-7), and Ca(2+)/calmodulin-dependent protein kinase II (CAM II kinase) inhibitor (KN-62), whereas P/Q- and N-type VDCC inhibitors showed no effects. In addition, nicotine exposure for 24 h induced [3H]nicotine binding to the particulate fractions of the neurons with an increased B(max) value and no changes in K(d). Under these conditions, the 30 mM KCl- and nicotine-induced 45Ca(2+) influx into the nicotine-treated neurons was significantly higher than those into non-treated neurons. These results suggest that the nicotine-stimulated increase in DBI mRNA expression is mediated by CAM II kinase activation resulting from the increase in intracellular Ca(2+) through L-type VDCCs subsequent to the neuronal membrane depolarization associated with nACh receptor activation.
我们使用原代培养的小鼠大脑皮质神经元，研究了尼古丁（0.1微摩尔）暴露24小时所诱导的地西泮结合抑制剂（DBI）及其mRNA表达增加的潜在机制。烟碱型乙酰胆碱（nACh）受体拮抗剂六甲铵可消除尼古丁（0.1微摩尔）诱导的DBI mRNA表达增加。稳定神经元膜的药物，包括河豚毒素（TTX）、普鲁卡因酰胺（一种Na(+)通道抑制剂）和局部麻醉剂（丁卡因和利多卡因），可剂量依赖性地抑制尼古丁诱导的DBI mRNA表达增加。尼古丁诱导的DBI mRNA表达增加受到L型电压依赖性Ca(2+)通道（VDCC）抑制剂如维拉帕米、钙调蛋白拮抗剂（W-7）和Ca(2+)/钙调蛋白依赖性蛋白激酶II（CAM II激酶）抑制剂（KN-62）的抑制，而P/Q型和N型VDCC抑制剂则无作用。此外，尼古丁暴露24小时可诱导[3H]尼古丁与神经元的微粒部分结合，B(max)值增加而K(d)无变化。在这些条件下，30 mM KCl和尼古丁诱导的45Ca(2+)流入尼古丁处理的神经元中的量显著高于未处理的神经元。这些结果表明，尼古丁刺激的DBI mRNA表达增加是由CAM II激酶激活介导的，该激活是由于与nACh受体激活相关的神经元膜去极化后通过L型VDCCs导致细胞内Ca(2+)增加所致。
