Molecular discrimination and transduction in singe olfactory and vomeronasal receptor cells

为了明确单个嗅觉细胞的气味特异性，在龟和蛙的单个嗅觉细胞中应用了不同的气味剂。结果表明，一个嗅觉细胞对不同的气味有反应。为了研究环GMP在嗅觉转导中的作用，我们将环GMP注射到龟的嗅觉细胞中。注射产生了向内的电流。我们得出结论，向内电流是通过环GMP依赖通道诱导的，表明环GMP特异性途径在龟嗅觉细胞中不存在。为了阐明犁鼻受体细胞的转导机制，我们将含有信息素的尿液应用于雌性大鼠犁鼻细胞。单个犁鼻细胞只对一种尿液有反应，表明单个犁鼻细胞具有很高的特异性。我们发现尿液中的活性成分是分子量低于5000的肽。我们还试图鉴定犁鼻细胞中的第二信使。向粪鼻细胞注射环状AMP无反应，但注射三磷酸肌醇（IP3）可诱导向内电流。IP3生成抑制剂或IP3门控通道阻滞剂的应用阻断了向内电流，表明IP3是粪鼻细胞中的第二信使。

In order to clarify the odor specificity of a single olfactory cell, various odorants were applied to single olfactory cells of turtle and frog. The results indicated that a single olfactory cell responds to various odorants. In order to examine roles of cyclic GMP in olfactory transduction, cyclic GMP was injected to turtle olfactory cells. The injection induced inward currents. We concluded that the inward currents were induced via cyclic AMP-dependent channel, indicating that pathway specific to cyclic GMP does not exit in turtle olfactory cells. In order to clarify the transduction mechanism of vomeronasal receptor cells, we applied urine, which contains pheromone(s), to rat female vomeronasal cells. Single vomeronasal cell responded only to one species of urine, indicating that a single vomeronasal cell has high specificity. We identified that active components in urine are peptides with molecular weight below 5000. We also tried to identify second messenger in vomeronasal cells. Injection of cyclic AMP to vomeronasal cells induced no response, but injection of inositol trisphosphate (IP3) induced inward currents. Application of inhibitors for generation of IP3 or a blocker of IP3-gated channel blocked the inward currents, suggesting that IP3 is a second messenger in vomeronasal cells.