Frank-Cannon Tamy C, Zeve Daniel R, Abbott Louise C
Texas A&M University, Department of Veterinary Integrative Biosciences, 4458 TAMU, College Station, TX 77843-4458, USA.
Brain Res. 2007 Apr 6;1140:96-104. doi: 10.1016/j.brainres.2005.10.082. Epub 2005 Dec 15.
Nitric oxide (NO) is a diffusible messenger molecule produced primarily by neuronal nitric oxide synthase (nNOS) in the central nervous system. Both nNOS expression and NO production are regulated by calcium ions. Leaner and tottering mice carry a mutation in the pore forming subunit (alpha1A) of P/Q-type voltage-gated calcium ion channels, which decreases calcium ion current through the affected channels and disrupts calcium homeostasis. We have previously shown that nNOS expression is altered in adult leaner and tottering cerebella. In addition, leaner and tottering mice have been shown to have abnormal cerebellar granule cell-Purkinje cell synapses and leaner cerebellar granule cells undergo abnormal apoptosis during early postnatal development. Since NO production has been linked to several developmental roles including neuronal cell death, synaptogenesis and neuronal cell survival, our objective was to evaluate the expression of nNOS in developing leaner and tottering cerebella. Our results show that nNOS is differentially expressed in leaner and tottering cerebella compared to wild type cerebella and compared to each other. In whole cerebella, Western blotting revealed a significant increase in nNOS expression at postnatal day 12 in tottering but not leaner or wild type cerebella. At the cellular level the NADPH-diaphorase marker for nNOS revealed a significant increase in nNOS expression in basket cell interneurons in both mutant mice. nNOS expression in granule cells in the internal granule cell layer in tottering mice was increased at P12, while granule cells of leaner mice exhibited decreased nNOS expression at P20. The changes in nNOS expression at P12 did not correlate with a change in overall NO production, but rather maintained wild type NO concentrations. These findings suggest that changes in nNOS expression in the leaner and tottering cerebella are compensatory in nature with NO most likely functioning as a calcium-regulated neuroprotective/neurotrophic factor in postnatal cerebellar development.
一氧化氮（NO）是一种可扩散的信使分子，主要由中枢神经系统中的神经元型一氧化氮合酶（nNOS）产生。nNOS的表达和NO的产生均受钙离子调节。伶鼠（leaner）和蹒跚鼠（tottering）携带P/Q型电压门控钙离子通道孔形成亚基（α1A）的突变，这会减少通过受影响通道的钙离子电流并破坏钙稳态。我们之前已经表明，成年伶鼠和蹒跚鼠的小脑nNOS表达会发生改变。此外，已证明伶鼠和蹒跚鼠具有异常的小脑颗粒细胞 - 浦肯野细胞突触，并且伶鼠的小脑颗粒细胞在出生后早期发育过程中会经历异常凋亡。由于NO的产生与包括神经元细胞死亡、突触形成和神经元细胞存活在内的多种发育作用相关，我们的目标是评估发育中的伶鼠和蹒跚鼠小脑nNOS的表达。我们的结果表明，与野生型小脑相比以及彼此相比，nNOS在伶鼠和蹒跚鼠小脑中的表达存在差异。在整个小脑中，蛋白质印迹法显示，在出生后第12天，蹒跚鼠小脑中nNOS表达显著增加，而伶鼠和野生型小脑则没有。在细胞水平上，nNOS的NADPH - 黄递酶标记显示，两种突变小鼠的篮状细胞中间神经元中nNOS表达显著增加。蹒跚鼠在出生后第12天，内颗粒层颗粒细胞中的nNOS表达增加，而伶鼠的颗粒细胞在出生后第20天nNOS表达降低。出生后第12天nNOS表达的变化与总体NO产生的变化无关，而是维持野生型NO浓度。这些发现表明，伶鼠和蹒跚鼠小脑中nNOS表达的变化本质上是代偿性的，NO很可能在出生后小脑发育中作为一种钙调节的神经保护/神经营养因子发挥作用。
