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Ionic basis of cold receptors in cultured sensory cells of rats

培养大鼠感觉细胞冷感受器的离子基础

基本信息

批准号：
12470009
负责人：
KOBAYSHI Shigeo
金额：
$ 8.83万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

When temperature (T) of skin decreases stepwise, cold fibers evoke transient efferent discharges, inducing cold sensation and heat-gain responses. Hence we have proposed that cold receptors at distal ends of cold fibers are thermostats to regulate skin T against cold. Here, with patch-clamp techniques, we studied the ionic basis of cold receptors in cultured dorsal root ganglion (DRG) neurons of rats, as a model of nerve endings. Cells that increased cytosolic Ca(2+) level in response to moderate cooling were identified as neurons with cold receptors. In whole-cell current-clamp recordings of these cells, in response to cooling, cold receptors evoked a dynamic receptor potential (RP), eliciting impulses briefly. In voltage-clamp recordings (-60 mV), step cooling induced an inward cold current (I(cold)) with mactivation, underlying the dynamic RP. Ca(2+) ions that entered into cells from extracellular side induced the inactivation. Analysis of the reversal potential implied that I(cold) was nonselective cation current with high Ca(2+) permeability. Threshold temperatures of cooling-induced Ca(2+) response and I(cold) were different primarily among cells. In outside-out patches, when T decreased, single nonselective cation channels became active at a critical T. This implies that a cold receptor is an ion channel and acts as the smallest thermostat. Because these thermal properties were consistent with that in cold fibers, we conclude that the same cold receptors exist at nerve endings and generate afferent impulses for cold sensation and heat-gain behaviors in response to cold.

当皮肤温度(T)逐步降低时，冷纤维引起短暂的传出放电，引起冷感觉和热增益反应。因此，我们提出冷纤维远端的冷受体是调节皮肤抗冷的恒温器。本研究采用膜片钳技术，以培养大鼠背根神经节（DRG）神经元为神经末梢模型，研究了冷受体的离子基础。细胞内Ca（2+）水平在适度冷却下升高的细胞被鉴定为具有冷受体的神经元。在这些细胞的全细胞电流钳记录中，作为对冷却的反应，冷受体诱发了一个动态受体电位（RP），引发了短暂的脉冲。在电压钳记录（-60 mV）中，阶跃冷却诱导了一个向内的冷流（I（冷）），并激活了动态RP。Ca（2+）离子从细胞外侧进入细胞，诱导细胞失活。反转电位分析表明，I（冷）是具有高Ca（2+）磁导率的非选择性阳离子电流。冷却诱导的Ca（2+）反应的阈温度和I（冷）的阈温度在细胞间主要存在差异。在由外到外的补片中，当T降低时，单个非选择性阳离子通道在临界T处变得活跃，这意味着冷受体是一个离子通道，充当最小的恒温器。由于这些热特性与冷纤维一致，我们得出结论，在神经末梢存在相同的冷感受器，并产生冷感觉和热获取行为的传入冲动，以应对寒冷。