Kleene Steven J
Department of Cancer and Cell Biology, University of Cincinnati, PO Box 670667, 231 Albert Sabin Way, Cincinnati, OH 45267-0667, USA.
Chem Senses. 2008 Nov;33(9):839-59. doi: 10.1093/chemse/bjn048. Epub 2008 Aug 14.
Most vertebrate olfactory receptor neurons share a common G-protein-coupled pathway for transducing the binding of odorant into depolarization. The depolarization involves 2 currents: an influx of cations (including Ca2+) through cyclic nucleotide-gated channels and a secondary efflux of Cl- through Ca2+-gated Cl- channels. The relation between stimulus strength and receptor current shows positive cooperativity that is attributed to the channel properties. This cooperativity amplifies the responses to sufficiently strong stimuli but reduces sensitivity and dynamic range. The odor response is transient, and prolonged or repeated stimulation causes adaptation and desensitization. At least 10 mechanisms may contribute to termination of the response; several of these result from an increase in intraciliary Ca2+. It is not known to what extent regulation of ionic concentrations in the cilium depends on the dendrite and soma. Although many of the major mechanisms have been identified, odor transduction is not well understood at a quantitative level.
大多数脊椎动物的嗅觉受体神经元共享一条常见的G蛋白偶联信号通路，用于将气味分子的结合转化为去极化。去极化涉及两种电流：阳离子（包括Ca2+）通过环核苷酸门控通道内流，以及Cl-通过Ca2+门控Cl-通道继发外流。刺激强度与受体电流之间的关系表现出正协同性，这归因于通道特性。这种协同性放大了对足够强刺激的反应，但降低了敏感性和动态范围。气味反应是短暂的，长时间或重复刺激会导致适应和脱敏。至少有10种机制可能导致反应终止；其中几种是由纤毛内Ca2+增加引起的。目前尚不清楚纤毛中离子浓度的调节在多大程度上依赖于树突和胞体。尽管已经确定了许多主要机制，但气味转导在定量水平上仍未得到很好的理解。
