Mody I, Heinemann U
Neurosci Lett. 1986 Aug 29;69(2):137-42. doi: 10.1016/0304-3940(86)90592-6.
Changes in extracellular free calcium concentration ([Ca2+]o) were measured with ion-selective microelectrodes in the dentate gyrus of the rat hippocampal slice preparation. Repetitive stimulation (20 Hz/10 s) of the perforant path or mossy fibers, or alternatively, iontophoresis of the excitatory amino acids N-methyl-D-aspartate (NMDA) or quisqualate (Quis) elicited decreases in [Ca2+]o (delta Ca2+) which were unequally distributed along the axis of the granule cells. Laminar profiles of the [Ca2+]o changes revealed marked differences between stimulus- and amino acid-induced responses. The delta Ca2+ induced by either anti- or orthodromic stimulation were relatively small (less than 0.15 mM) and were found to be maximal at the cell body layer (stratum granulosum). In contrast, the excitatory amino acids NMDA and Quis evoked large delta Ca2+ (greater than 1.2 mM) which were maximal at dendritic sites, 100 microns away from the cell body layer in the inner stratum moleculare. The effect of NMDA was reversibly blocked by 2-amino-5-phosphonovaleric acid without antagonism of the synaptic responses or the stimulus-induced changes in [Ca2+]o. Therefore, under normal conditions, NMDA receptors appear not to participate in synaptically induced delta Ca2+ in the dentate gyrus.
采用离子选择性微电极，测定大鼠海马脑片制备物齿状回中细胞外游离钙浓度（[Ca2+]o）的变化。对穿通通路或苔藓纤维进行重复刺激（20 Hz/10 s），或者对兴奋性氨基酸N-甲基-D-天冬氨酸（NMDA）或quisqualate（Quis）进行离子电泳，均可引起[Ca2+]o（ΔCa2+）降低，且沿颗粒细胞轴的分布不均匀。[Ca2+]o变化的层状分布图显示，刺激诱导反应和氨基酸诱导反应之间存在显著差异。由逆行或顺行刺激诱导的ΔCa2+相对较小（小于0.15 mM），且在细胞体层（颗粒层）达到最大值。相比之下，兴奋性氨基酸NMDA和Quis诱发的ΔCa2+较大（大于1.2 mM），在树突部位达到最大值，该部位位于分子层内层，距离细胞体层100微米。NMDA的作用可被2-氨基-5-磷酸戊酸可逆性阻断，而不影响突触反应或刺激诱导的[Ca2+]o变化。因此，在正常情况下，NMDA受体似乎不参与齿状回中突触诱导的ΔCa2+。
