Kim Yuil, Trussell Laurence O
Oregon Hearing Research Center/ Vollum Institute, Mail Code L-335A, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA.
J Neurophysiol. 2007 Feb;97(2):1705-25. doi: 10.1152/jn.00536.2006.
Cartwheel cells are glycinergic interneurons that modify somatosensory input to the dorsal cochlear nucleus. They are characterized by firing of mixtures of both simple and complex action potentials. To understand what ion channels determine the generation of these two types of spike waveforms, we recorded from cartwheel cells using the gramicidin perforated-patch technique in brain slices of mouse dorsal cochlear nucleus and applied channel-selective blockers. Complex spikes were distinguished by whether they arose directly from a negative membrane potential or later during a long depolarization. Ca(2+) channels and Ca(2+)-dependent K(+) channels were major determinants of complex spikes. Onset complex spikes required T-type and possibly R-type Ca(2+) channels and were shaped by BK and SK K(+) channels. Complex spikes arising later in a depolarization were dependent on P/Q- and L-type Ca(2+) channels as well as BK and SK channels. BK channels also contributed to fast repolarization of simple spikes. Simple spikes featured an afterdepolarization that is probably the trigger for complex spiking and is shaped by T/R-type Ca(2+) and SK channels. Fast spikes were dependent on Na(+) channels; a large persistent Na(+) current may provide a depolarizing drive for spontaneous activity in cartwheel cells. Thus the diverse electrical behavior of cartwheel cells is determined by the interaction of a wide variety of ion channels with a prominent role played by Ca(2+).
车轮状细胞是甘氨酸能中间神经元，可调节躯体感觉输入至蜗背侧核。它们的特征是发放简单动作电位和复合动作电位的混合信号。为了解哪些离子通道决定这两种类型的尖峰波形的产生，我们在小鼠蜗背侧核脑片中使用短杆菌肽穿孔膜片钳技术记录车轮状细胞，并应用通道选择性阻滞剂。复合尖峰通过它们是直接从负膜电位产生还是在长时间去极化后期产生来区分。Ca(2+)通道和Ca(2+)依赖性K(+)通道是复合尖峰的主要决定因素。起始复合尖峰需要T型以及可能的R型Ca(2+)通道，并由BK和SK K(+)通道塑造。在去极化后期出现的复合尖峰依赖于P/Q型和L型Ca(2+)通道以及BK和SK通道。BK通道也有助于简单尖峰的快速复极化。简单尖峰具有一个去极化后电位，这可能是复合尖峰发放的触发因素，并由T/R型Ca(2+)和SK通道塑造。快速尖峰依赖于Na(+)通道；一个大的持续性Na(+)电流可能为车轮状细胞的自发活动提供去极化驱动。因此，车轮状细胞多样的电活动是由多种离子通道的相互作用决定的，其中Ca(2+)起着突出作用。
