Stringer Janet L, Mukherjee Kakali, Xiang Ting, Xu Kaiping
Department of Pharmacology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, United States.
Epilepsy Res. 2007 May;74(2-3):155-62. doi: 10.1016/j.eplepsyres.2007.03.005. Epub 2007 Apr 16.
Astrocytes have been suggested to regulate the extracellular calcium concentration (Ca(2+)), but this has not been thoroughly investigated. Adult, male Sprague-Dawley rats were used to record changes in Ca(2+) in the hippocampus during epileptiform activity. Maximal decreases in Ca(2+) in CA1 were measured in the pyramidal cell layer during 20 Hz, 20s stimulus trains to the contralateral CA3 region. Maximal decreases in Ca(2+) in the dentate gyrus were measured when maximal dentate activation had appeared-irrespective of the location, frequency or duration of the stimulation. Maximal decreases were 36% greater in the dentate gyrus than in CA1. During prolonged discharges, Ca(2+) recovered partially towards the baseline in both hippocampal regions. To investigate the role of astrocytes, local injections of fluorocitrate (FC), a metabolic toxin selectively taken up by astrocytes, were used. FC (0.1, 0.25 or 0.5mM FC), but not vehicle (2 microl), caused a small, but significant decrease in the maximal changes in CA1, but an increase in the dentate gyrus. The results suggest that maximal decreases in Ca(2+) occur in the hippocampus in response to burst firing of neurons and that astrocytes play a minimal role in the regulation of Ca(2+) during epileptiform activity.
已有研究表明星形胶质细胞可调节细胞外钙浓度（Ca(2+)），但尚未对此进行全面研究。本研究使用成年雄性Sprague-Dawley大鼠记录癫痫样活动期间海马区Ca(2+)的变化。在对侧CA3区进行20Hz、20s的刺激串时，测量CA1区锥体细胞层Ca(2+)的最大降幅。当齿状回出现最大激活时测量其Ca(2+)的最大降幅，而不考虑刺激的位置、频率或持续时间。齿状回的最大降幅比CA1区大36%。在长时间放电期间，两个海马区的Ca(2+)均部分恢复至基线水平。为研究星形胶质细胞的作用，采用局部注射氟代柠檬酸（FC）的方法，FC是一种被星形胶质细胞选择性摄取的代谢毒素。FC（0.1、0.25或0.5mM FC）而非溶剂（2微升）可导致CA1区最大变化出现小幅但显著的下降，但在齿状回中却出现增加。结果表明，神经元爆发式放电会使海马区Ca(2+)出现最大降幅，且星形胶质细胞在癫痫样活动期间对Ca(2+)的调节作用最小。
