Skov Jane, Andreasen Mogens, Nedergaard Steen
Institute of Physiology and Biophysics, Department of Physiology, University of Aarhus, Denmark.
Brain Res. 2006 Jun 22;1096(1):61-9. doi: 10.1016/j.brainres.2006.04.041. Epub 2006 May 24.
Long-term application of Cs(+) (5 mM) induces an epileptiform field potential (Cs-FP) in area CA1 of the rat hippocampus, which is independent of N-methyl-D-aspartate (NMDA) and non-NMDA glutamate receptors and gamma-aminobutyric acid (GABA)(A) receptors. To gain insight into possible mechanisms for the induction of the Cs-FP, we investigated the postnatal development of the response. In brain slices prepared from rats at different ages, the Cs-FP was evoked by stimulation of the Schaffer-collateral-commisural pathway. We found that expression of this potential was clearly dependent on the postnatal age. Thus, the Cs-FP was completely absent at 1 week of age. By 2 weeks, a reduced form of the response was observed, whereas slices taken from 3-week-old rats, displayed full Cs-FP, which were indistinguishable in size and shape from the adult form. In the presence of 4-aminopyridine, potentials resembling the Cs-FP were evoked. These potentials showed a similar age-dependency as the Cs-FP. The Na(+)/K(+) pump inhibitor dihydroouabain (DHO), when present during wash-in of Cs(+), gave a partial block of the Cs-FP in adult slices. This effect was not seen when DHO was applied after development of the Cs-FP. The data indicate that the processes necessary for expression of the Cs-PF are absent at birth and develop during the second postnatal week. We propose that the Cs-FP depends on Cs(+) entry into presynaptic neurons, and that the Na(+)/K(+) pump contributes to this transport of Cs(+). The observed age-dependency could therefore, in part, reflect the delayed development of the Na(+)/K(+) pump.
长期应用铯离子（5毫摩尔）可在大鼠海马体CA1区诱导出癫痫样场电位（Cs-FP），该电位独立于N-甲基-D-天冬氨酸（NMDA）和非NMDA谷氨酸受体以及γ-氨基丁酸（GABA）A受体。为深入了解诱导Cs-FP的可能机制，我们研究了该反应的出生后发育情况。在不同年龄大鼠制备的脑片中，通过刺激Schaffer侧支-连合通路诱发Cs-FP。我们发现该电位的表达明显依赖于出生后年龄。因此，在1周龄时Cs-FP完全不存在。到2周龄时，观察到反应的一种减弱形式，而取自3周龄大鼠的脑片则显示出完整的Cs-FP，其大小和形状与成年形式无明显差异。在存在4-氨基吡啶的情况下，诱发了类似于Cs-FP的电位。这些电位显示出与Cs-FP相似的年龄依赖性。钠/钾泵抑制剂二氢哇巴因（DHO）在铯离子冲洗过程中存在时，可使成年脑片中的Cs-FP部分受阻。当在Cs-FP形成后应用DHO时，未观察到这种效应。数据表明，出生时不存在表达Cs-PF所需的过程，这些过程在出生后第二周发育。我们提出Cs-FP依赖于铯离子进入突触前神经元，并且钠/钾泵有助于铯离子的这种转运。因此，观察到的年龄依赖性可能部分反映了钠/钾泵发育的延迟。
