Ca2+-independent muscarinic excitation of rat medial entorhinal cortex layer V neurons
Ca2+-independent muscarinic excitation of rat medial entorhinal cortex layer V neurons
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DOI：
10.1111/j.1460-9568.2003.03050.x
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发表时间：
2003-12-01
影响因子：
3.4
通讯作者：
Müller, W
中科院分区：
文献类型：
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作者：
Egorov, AV;Angelova, PR;Müller, W
内嗅皮层（EC）V层神经元的胆碱能激活在内侧颞叶记忆系统和颞叶癫痫的病理生理学中起着至关重要的作用。在这里，我们证明了毒蕈碱激活的局部应用卡巴胆碱EC层V神经元去极化，并诱导癫痫样活动在大鼠脑片。这些神经节样爆发与体细胞[Ca 2 +]（i）增加293 +/- 82 nM相关，并被谷氨酸受体拮抗剂CNQX和APV阻断。毒蕈碱激活并不直接引起[Ca 2 +]（i）增加，但阈下和阈上去极化。功能性轴突映射显示局部轴突分支以及轴突侧支上升到第II层和第III层。在阻断离子型谷氨酸能AMPA和NMDA受体期间，卡巴胆碱使V层神经元去极化+7.5 +/- 3.4 mV。这种直接毒蕈碱去极化与电导增加35 +/- 10.3%（+4.3 +/- 1.25 nS）相关。细胞内缓冲的[Ca 2 +]（i）变化并不阻断这种去极化，但延长了动作电位时程，降低了动作电位放电的适应性。毒蕈碱去极化既不阻断细胞内钙离子缓冲（EGTA或BAPTA）与非特异性钙通道抑制Ni+（1 mM），也不通过Ba 2+（1 mM），也不是在抑制h-电流2 mM Cs+。在全细胞膜片钳记录中，当Cs+完全取代K+时，毒蕈碱电流在约-45 mV和-5 mV处发生逆转。因此，EC层V神经元的毒蕈碱去极化似乎主要由非特异性阳离子通道的Ca 2+非依赖性激活介导，所述非特异性阳离子通道传导K+约3倍以及Na+。
Cholinergic activation of entorhinal cortex (EC) layer V neurons plays a crucial role in the medial temporal lobe memory system and in the pathophysiology of temporal lobe epilepsy. Here, we demonstrate that muscarinic activation by focal application of carbachol depolarizes EC layer V neurons and induces epileptiform activity in rat brain slices. These seizure-like bursts are associated with a somatic [Ca2+](i) increase of 293 +/- 82 nM and are blocked by the glutamate receptor antagonists CNQX and APV. Muscarinic activation did not directly evoke a [Ca2+](i) increase, but subthreshold and suprathreshold depolarization did. Functional axon mapping revealed local axon branching as well as axon collaterals ascending to layers II and III. During blockade of ionotropic glutamatergic AMPA and NMDA receptors, carbachol depolarized layer V neurons by +7.5 +/- 3.4 mV. This direct muscarinic depolarization was associated with a conductance increase of 35 +/- 10.3% (+4.3 +/- 1.25 nS). Intracellular buffering of [Ca2+](i) changes did not block this depolarization, but prolonged action potential duration and reduced adaptation of action potential firing. The muscarinic depolarization was neither blocked by combining intracellular Ca2+-buffering (EGTA or BAPTA) with non-specific Ca2+-channel inhibition by Ni+ (1 mM), nor by Ba2+ (1 mM) nor during inhibition of the h-current by 2 mM Cs+. In whole-cell patch-clamp recording, reversal of the muscarinic current occurred at about -45 mV and -5 mV with complete substitution of intrapipette K+ with Cs+. Thus, muscarinic depolarization of EC layer V neurons appears to be primarily mediated by Ca2+-independent activation of non-specific cation channels that conduct K+ about three times as well as Na+.