Thomson A M
Neuroscience. 1984 Nov;13(3):761-7. doi: 10.1016/0306-4522(84)90094-0.
The Ca2+ dependence of suprachiasmatic firing patterns was studied in isolated hypothalamic slices. Single neurones were first recorded in a standard artificial cerebrospinal fluid and then followed through a change to a medium in which the Ca2+ was replaced with Mg2+, Co2+ or Mn2+. These test media caused disruption of the normal, slow, regular firing patterns of suprachiasmatic neurones. Some interspike intervals were shorter and some longer than any recorded under normal conditions, for a given firing frequency. In the absence of Ca2+, these cells could not be driven to fire more regularly as they fired more rapidly during glutamate applications. In contrast, in the presence of Ca2+ more slowly and irregularly firing suprachiasmatic cells can be driven to fire regularly if their firing rate is increased. The effects of these test media were reversible. When Ca2+ was replaced with Ba2+, a bursting pattern of discharge resulted. Periods of high frequency discharge, possibly superimposed on Ba2+ spikes, alternated with periods of slow, regular firing or silence. It is concluded that Ca2+ is necessary for the maintenance of regular firing in suprachiasmatic neurones. The possibility that Ca2+ channels similar to those present in other slow, regularly firing central neurones, play an important role in suprachiasmatic activity, is discussed.
在分离的下丘脑切片中研究了视交叉上核放电模式对钙离子的依赖性。首先在标准人工脑脊液中记录单个神经元，然后将其置于钙离子被镁离子、钴离子或锰离子取代的介质中继续记录。这些测试介质会破坏视交叉上核神经元正常、缓慢、规则的放电模式。对于给定的放电频率，一些峰间间隔比正常情况下记录的短，一些则更长。在无钙离子的情况下，这些细胞在应用谷氨酸时放电更快，但无法被驱动更规则地放电。相反，在有钙离子的情况下，如果放电速率增加，放电更慢且不规则的视交叉上核细胞可以被驱动规则放电。这些测试介质的作用是可逆的。当钙离子被钡离子取代时，会产生一种爆发性放电模式。高频放电期（可能叠加在钡离子尖峰上）与缓慢、规则放电期或静息期交替出现。结论是钙离子对视交叉上核神经元维持规则放电是必需的。文中还讨论了类似于其他缓慢、规则放电的中枢神经元中存在的钙离子通道在视交叉上核活动中起重要作用的可能性。
