Alavez Silvestre, Blancas Sugela, Morán Julio
Departamento de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México D. F., México.
Neurosci Lett. 2006 May 8;398(3):241-5. doi: 10.1016/j.neulet.2006.01.002. Epub 2006 Feb 15.
Cerebellar granule neurons (CGN) are the most abundant neuronal type in the cerebellum. During development, these cells migrate from the external to the internal granule layer (IGL), where they receive excitatory glutamatergic and cholinergic contacts from mossy fibers. During this period of development a large proportion of CGN are eliminated via apoptosis. In vitro studies have demonstrated that when CGN are obtained from rats at postnatal day 8 (P8), the sustained activation of N-methyl-D-aspartate (NMDA) receptor at 2-4 days in vitro rescues neurons from cell death. The NMDA action on cultured CGN could mimic the in vivo actions of the transient activation of the glutamate receptors by the transmitter released by mossy fibers by P12. However, some results suggest that glutamate stimulation could be relevant for CGN at earlier stages of development. In this study we evaluated the effect of NMDA receptor stimulation or blockade on the cell death of both in vivo and cultured CGN obtained from P2 to P8 rats. Our results showed that the blockade of NMDA receptors with the antagonists D,L-2-amino-5-phosphonovaleric acid or dizocilpine (MK-801) reduces cell survival to 20-40%, whereas NMDA treatment increases neuronal survival by approximately 50-60%. In vivo, the treatment with MK-801 reduced the number of apoptotic CGN in the molecular layer (ML) from P5 to P8. These results suggest that NMDA receptor stimulation plays a critical role in the regulation of CGN death during the first week of rat cerebellar development.
小脑颗粒神经元（CGN）是小脑中数量最多的神经元类型。在发育过程中，这些细胞从外颗粒层迁移至内颗粒层（IGL），在那里它们接受来自苔藓纤维的兴奋性谷氨酸能和胆碱能接触。在这个发育阶段，很大一部分CGN通过凋亡被清除。体外研究表明，当在出生后第8天（P8）从大鼠获取CGN时，体外培养2 - 4天时N - 甲基 - D - 天冬氨酸（NMDA）受体的持续激活可使神经元免于细胞死亡。NMDA对培养的CGN的作用可模拟在出生后第12天苔藓纤维释放的递质对谷氨酸受体的短暂激活的体内作用。然而，一些结果表明谷氨酸刺激在CGN发育的早期阶段可能是相关的。在本研究中，我们评估了NMDA受体刺激或阻断对从P2至P8大鼠获取的体内和体外培养的CGN细胞死亡的影响。我们的结果表明，用拮抗剂D，L - 2 - 氨基 - 5 -磷酸戊酸或地卓西平（MK - 801）阻断NMDA受体会使细胞存活率降至20 - 40%，而NMDA处理可使神经元存活率提高约50 - 60%。在体内，用MK - 801处理可减少从P5至P8分子层（ML）中凋亡的CGN数量。这些结果表明，NMDA受体刺激在大鼠小脑发育的第一周对CGN死亡的调节中起关键作用。
