Mejia-Gervacio S, Hounsgaard J, Diaz-Muñoz M
Dept. de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Apartado Postal 1-1141, Juriquilla, Querétaro, Mexico.
Neuroscience. 2004;123(1):123-30. doi: 10.1016/j.neuroscience.2003.08.049.
Generation of plateau potentials in spinal motoneurons depends on activation of voltage sensitive L-type Ca(2+) channels. These channels are facilitated by metabotropic receptors known to promote release of Ca(2+) from intracellular stores. The aim of this study is to determine if Ca(2+)-release receptors in the endoplasmic reticulum (ER) that are sensitive to ryanodine (RyRs) and to inositol triphosphate receptors (IP(3)Rs) contribute to the generation of plateau potentials. The effects of antagonists to RyRs, IP(3)Rs and phospholipase C (PLC) were tested on discharge patterns associated with plateau potentials in motoneurons in slices from the spinal cord of the turtle. Plateau-related discharge patterns, un-facilitated or facilitated by agonists for group I glutamate metabotropic receptors, muscarine-sensitive cholinergic receptors or L-type Ca(2+) channels were inhibited by blockade of RyRs. In contrast, antagonists of IP(3)Rs or PLC preferentially inhibited plateau-related discharge patterns when facilitated by activation of metabotropic receptors but in only half of the cells when promoted in the absence of metabotropic facilitators. Our findings show that RyRs and IP(3)Rs regulate the generation of plateau potentials in motoneurons and suggest that RyRs may be directly involved with activation of the plateau potential.
脊髓运动神经元中平台电位的产生依赖于电压敏感性L型Ca(2+)通道的激活。这些通道可被已知能促进细胞内钙库释放Ca(2+)的代谢型受体所促进。本研究的目的是确定内质网（ER）中对兰尼碱（RyRs）和肌醇三磷酸受体（IP(3)Rs）敏感的Ca(2+)释放受体是否有助于平台电位的产生。测试了RyRs、IP(3)Rs和磷脂酶C（PLC）拮抗剂对乌龟脊髓切片中运动神经元与平台电位相关的放电模式的影响。与平台相关的放电模式，无论是否被I组谷氨酸代谢型受体、毒蕈碱敏感胆碱能受体或L型Ca(2+)通道的激动剂所促进，在RyRs被阻断时均受到抑制。相比之下，IP(3)Rs或PLC拮抗剂在代谢型受体激活促进时优先抑制与平台相关的放电模式，但在无代谢型促进剂时促进的情况下，仅在一半的细胞中起作用。我们的研究结果表明，RyRs和IP(3)Rs调节运动神经元中平台电位的产生，并提示RyRs可能直接参与平台电位的激活。
