Schweizer Felix E, Savin David, Luu Cindy, Sultemeier David R, Hoffman Larry F
Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095, USA.
J Comp Neurol. 2009 Nov 10;517(2):134-45. doi: 10.1002/cne.22148.
Voltage- and calcium-activated potassium channels (BK) are important regulators of neuronal excitability. BK channels seem to be crucial for frequency tuning in nonmammalian vestibular and auditory hair cells. However, there are a paucity of data concerning BK expression in mammalian vestibular hair cells. We therefore investigated the localization of BK channels in mammalian vestibular hair cells, specifically in rat vestibular neuroepithelia. We find that only a subset of hair cells in the utricle and the crista ampullaris express BK channels. BK-positive hair cells are located mainly in the medial striolar region of the utricle, where they constitute at most 12% of hair cells, and in the central zone of the horizontal crista. A majority of BK-positive hair cells are encapsulated by a calretinin-positive calyx defining them as type I cells. The remainder are either type I cells encapsulated by a calretinin-negative calyx or type II hair cells. Surprisingly, the number of BK-positive hair cells in the utricle peaks in juvenile rats and declines in early adulthood. BK channels were not found in vestibular afferent dendrites or somata. Our data indicate that BK channel expression in the mammalian vestibular system differs from the expression pattern in the mammalian auditory and the nonmammalian vestibular system. The molecular diversity of vestibular hair cells indicates a functional diversity that has not yet been fully characterized. The predominance of BK-positive hair cells within the medial striola of juvenile animals suggests that they contribute to a scheme of highly lateralized coding of linear head movements during late development.
电压门控和钙激活钾通道（BK）是神经元兴奋性的重要调节因子。BK通道似乎对非哺乳动物前庭和听觉毛细胞的频率调谐至关重要。然而，关于BK通道在哺乳动物前庭毛细胞中的表达数据却很少。因此，我们研究了BK通道在哺乳动物前庭毛细胞中的定位，特别是在大鼠前庭神经上皮中的定位。我们发现，只有椭圆囊和壶腹嵴中的一部分毛细胞表达BK通道。BK阳性毛细胞主要位于椭圆囊的内侧纹状区，在那里它们最多占毛细胞的12%；以及水平嵴的中央区。大多数BK阳性毛细胞被钙视网膜蛋白阳性的花萼包裹，这表明它们是I型细胞。其余的要么是被钙视网膜蛋白阴性花萼包裹的I型细胞，要么是II型毛细胞。令人惊讶的是，椭圆囊中BK阳性毛细胞的数量在幼年大鼠中达到峰值，并在成年早期下降。在前庭传入神经树突或胞体中未发现BK通道。我们的数据表明，哺乳动物前庭系统中BK通道的表达与哺乳动物听觉系统和非哺乳动物前庭系统中的表达模式不同。前庭毛细胞的分子多样性表明其功能多样性尚未得到充分表征。幼年动物内侧纹状区内BK阳性毛细胞的优势表明，它们在发育后期对线性头部运动的高度侧向化编码机制有贡献。
