Cigola E, Volpe B T, Lee J W, Franzen L, Baker H
Cornell University Medical College at The Burke Medical Research Institute, White Plains, New York, 10605, USA.
J Neurosci. 1998 Oct 1;18(19):7638-49. doi: 10.1523/JNEUROSCI.18-19-07638.1998.
Sensory activity mediates regulation of tyrosine hydroxylase (TH), the first enzyme in the dopamine biosynthetic pathway, in the rodent olfactory bulb. The current studies established for the first time primary cultures of neonatal mouse olfactory bulb expressing TH and tested whether L-type calcium channels mediate the activity-dependent regulation of the dopamine phenotype. After 1 d in vitro (DIV), a small population of TH-immunostained neurons that lacked extensive processes could be demonstrated. After an additional 2 DIV in serum-free medium, the number of TH neurons had doubled, and they exhibited long interdigitating processes. Membrane depolarization for 48 hr with 50 mM KCl produced a further 2.4-fold increase in the number of TH-immunoreactive neurons compared with control cultures. Increased TH neuron number required at least 36 hr of exposure to KCl. Forskolin, which increases intracellular cAMP levels, induced a 1.5- to 1.6-fold increase in the number of TH-immunostained neurons. Combined treatment with KCl and forskolin was not additive. Nifedipine, an L-type calcium channel blocker, completely prevented the depolarization-mediated increase in TH expression but did not block the response to forskolin. Treatment with Bay K8644, an L-type calcium channel agonist, also significantly increased the number of TH-expressing neurons. Depolarization also induced alterations in neuritic outgrowth, resulting in a stellate versus an elongate morphology that, in contrast, was not prevented by nifedipine. These results are the first demonstration that in vitro, as in vivo, depolarization increases TH expression in olfactory bulb and that L-type calcium channels mediate this activity-dependent regulation of the dopamine phenotype.
感觉活动介导啮齿动物嗅球中酪氨酸羟化酶（TH）的调节，TH是多巴胺生物合成途径中的第一种酶。目前的研究首次建立了表达TH的新生小鼠嗅球原代培养物，并测试了L型钙通道是否介导多巴胺表型的活性依赖性调节。体外培养1天（DIV）后，可以证明一小部分缺乏广泛突起的TH免疫染色神经元。在无血清培养基中再培养2天DIV后，TH神经元的数量增加了一倍，并且它们呈现出长的相互交错的突起。与对照培养物相比，用50 mM KCl进行48小时的膜去极化使TH免疫反应性神经元的数量进一步增加了2.4倍。TH神经元数量的增加至少需要36小时暴露于KCl。福斯高林可增加细胞内cAMP水平，可使TH免疫染色神经元的数量增加1.5至1.6倍。KCl和福斯高林联合治疗没有相加作用。L型钙通道阻滞剂硝苯地平完全阻止了去极化介导的TH表达增加，但没有阻断对福斯高林的反应。L型钙通道激动剂Bay K8644治疗也显著增加了表达TH的神经元数量。去极化还诱导了神经突生长的改变，导致星形与细长形态，相比之下，硝苯地平并未阻止这种形态改变。这些结果首次证明，在体外，与体内一样，去极化会增加嗅球中TH的表达，并且L型钙通道介导多巴胺表型的这种活性依赖性调节。
