Richter H, Heinemann U, Eder C
Johannes-Müller-Institut für Physiologie, Abt. Neurophysiologie, Humboldt Universität zu Berlin, Tucholskystr. 2, D 10117, Berlin, Germany.
Neurosci Lett. 2000 Mar 3;281(1):33-6. doi: 10.1016/s0304-3940(00)00794-1.
Properties of hyperpolarization-activated cation currents (I(h)) were investigated in neurons of juvenile rat entorhinal cortex using the patch-clamp technique. A rat brain slice preparation containing the entorhinal cortex was used for whole-cell recordings of I(h) in pyramidal cells from layer IV and in stellate cells from layer II of the entorhinal cortex. In both stellate and pyramidal cells, I(h) activated at potentials more negative than -60 mV and did not show any time-dependent inactivation. Half-maximal activation of I(h) was achieved at -95.3 mV in pyramidal cells and at -95.0 mV in stellate cells. The channels were permeable for sodium and potassium ions. I(h) of pyramidal and stellate neurons was reduced by about 50% in the presence of 100 microM ZD7288. Extracellularly applied 1 mM Cs(+) decreased I(h) of pyramidal cells by 92%, whereas I(h) of stellate cells was only reduced by 70%. In both pyramidal and stellate neurons, I(h) was not significantly changed during the application of 1 mM Ba(2+). 8-Bromo-c-AMP increased amplitudes of I(h) in stellate cells, while I(h) of pyramidal cells remained unchanged. It is suggested that different types of hyperpolarization-activated cation channels are expressed in pyramidal and stellate cells of the entorhinal cortex.
采用膜片钳技术研究了幼年大鼠内嗅皮质神经元中超极化激活阳离子电流（I(h)）的特性。使用包含内嗅皮质的大鼠脑片标本，对来自内嗅皮质IV层的锥体细胞和II层的星状细胞进行I(h)的全细胞记录。在星状细胞和锥体细胞中，I(h)均在比-60 mV更负的电位时激活，且未表现出任何时间依赖性失活。锥体细胞中I(h)的半数最大激活电位为-95.3 mV，星状细胞中为-95.0 mV。这些通道对钠离子和钾离子通透。在存在100 microM ZD7288的情况下，锥体细胞和星状细胞的I(h)降低约50%。细胞外施加1 mM Cs(+)使锥体细胞的I(h)降低92%，而星状细胞的I(h)仅降低70%。在锥体细胞和星状神经元中，施加1 mM Ba(2+)期间I(h)均无显著变化。8-溴-c-AMP增加星状细胞中I(h)的幅度，而锥体细胞的I(h)保持不变。提示在内嗅皮质的锥体细胞和星状细胞中表达了不同类型的超极化激活阳离子通道。
