Program in Communication Science, Department of Anesthesiology and Pain Medicine, School of Medicine, University of California Davis, Davis, California, USA.
PLoS One. 2011;6(12):e29005. doi: 10.1371/journal.pone.0029005. Epub 2011 Dec 22.
Spontaneous action potentials have been described in developing sensory systems. These rhythmic activities may have instructional roles for the functional development of synaptic connections. The importance of spontaneous action potentials in the developing auditory system is underpinned by the stark correlation between the time of auditory system functional maturity, and the cessation of spontaneous action potentials. A prominent K(+) current that regulates patterning of action potentials is I(A). This current undergoes marked changes in expression during chicken hair cell development. Although the properties of I(A) are not normally classified as Ca(2+)-dependent, we demonstrate that throughout the development of chicken hair cells, I(A) is greatly reduced by acute alterations of intracellular Ca(2+). As determinants of spike timing and firing frequency, intracellular Ca(2+) buffers shift the activation and inactivation properties of the current to more positive potentials. Our findings provide evidence to demonstrate that the kinetics and functional expression of I(A) are tightly regulated by intracellular Ca(2+). Such feedback mechanism between the functional expression of I(A) and intracellular Ca(2+) may shape the activity of spontaneous action potentials, thus potentially sculpting synaptic connections in an activity-dependent manner in the developing cochlea.
在发育中的感觉系统中已经描述了自发性动作电位。这些有节奏的活动可能对突触连接的功能发育具有指导作用。自发性动作电位在发育中的听觉系统中的重要性是由听觉系统功能成熟的时间和自发性动作电位停止之间的明显相关性来支持的。调节动作电位模式的主要 K(+)电流是 I(A)。这种电流在鸡毛细胞发育过程中的表达发生了显著变化。尽管 I(A)的特性通常不被归类为 Ca(2+)依赖性，但我们证明，在鸡毛细胞的整个发育过程中，急性改变细胞内 Ca(2+)会大大减少 I(A)。作为尖峰时间和发射频率的决定因素，细胞内 Ca(2+)缓冲剂将电流的激活和失活特性转移到更正的电位。我们的发现提供了证据，证明 I(A)的动力学和功能表达受到细胞内 Ca(2+)的严格调节。I(A)的功能表达和细胞内 Ca(2+)之间的这种反馈机制可能会影响自发性动作电位的活动，从而以一种依赖于活动的方式潜在地塑造发育中的耳蜗中的突触连接。
