Action potentials and chemosensitive conductances in the dendrites of olfactory neurons suggest new features for odor transduction.
Action potentials and chemosensitive conductances in the dendrites of olfactory neurons suggest new features for odor transduction.
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DOI：
10.1085/jgp.103.2.181
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发表时间：
1994-02
期刊：
影响因子：
--
通讯作者：
Dionne VE
中科院分区：
文献类型：
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作者：
Dubin AE;Dionne VE
气味通过改变单个长树突纤毛末端的膜电导来影响嗅觉神经元的兴奋性。增加嗅觉神经元对气味敏感性的一种机制是它们的树突支持动作电位。我们首次发现，从mudpuppy Necturus maculosus分离的嗅树突含有高密度的电压激活的Na+通道，并产生Na依赖性动作电位响应去极化电流脉冲。此外，所有需要的步骤，在转导过程中开始与气味检测和动作电位引发的高潮发生在纤毛树突。我们以前已经表明，气味可以调节完整的嗅觉神经元中的Cl-和K+电导，产生兴奋和抑制。在这里，我们表明，这两个电导也存在于孤立的，纤毛树突附近的气味结合的网站，他们调制的气味，他们影响神经元的兴奋性。电压激活的Cl-电流被4，4 '-diisothiocyanatostilbene-2，2' disulfonic acid和尼氟灭酸阻断，纤毛树突中的平均密度比索马中的高5倍以上，而电压激活的K+电流被细胞内Cs+抑制，平均分布在整个细胞中更均匀。当纤毛，化学敏感的树突刺激的气味牛磺酸，反应类似于在完整的细胞中看到的：Cl-电流增加，在一些树突，而在其他Cl-或K+电流减少，和响应冲洗在全细胞记录。使用细胞上电压斜坡方案和延迟应用通道阻断剂，发现浸泡在生理盐水中的完整神经元的Cl-平衡电位为-45 mV。我们假设，一些气味的转导是由第二信使介导的调制的静息膜电导（而不是一个专门的发电机电导）在纤毛或顶端区域的树突，并显示这可能会改变放电频率的嗅觉神经元。
Odors affect the excitability of an olfactory neuron by altering membrane conductances at the ciliated end of a single, long dendrite. One mechanism to increase the sensitivity of olfactory neurons to odorants would be for their dendrites to support action potentials. We show for the first time that isolated olfactory dendrites from the mudpuppy Necturus maculosus contain a high density of voltage-activated Na+ channels and produce Na-dependent action potentials in response to depolarizing current pulses. Furthermore, all required steps in the transduction process beginning with odor detection and culminating with action potential initiation occur in the ciliated dendrite. We have previously shown that odors can modulate Cl- and K+ conductances in intact olfactory neurons, producing both excitation and inhibition. Here we show that both conductances are also present in the isolated, ciliated dendrite near the site of odor binding, that they are modulated by odors, and that they affect neuronal excitability. Voltage- activated Cl- currents blocked by 4,4'-diisothiocyanatostilbene-2,2' disulfonic acid and niflumic acid were found at greater than five times higher average density in the ciliated dendrite than in the soma, whereas voltage-activated K+ currents inhibited by intracellular Cs+ were distributed on average more uniformly throughout the cell. When ciliated, chemosensitive dendrites were stimulated with the odorant taurine, the responses were similar to those seen in intact cells: Cl- currents were increased in some dendrites, whereas in others Cl- or K+ currents were decreased, and responses washed out during whole-cell recording. The Cl- equilibrium potential for intact neurons bathed in physiological saline was found to be -45 mV using an on-cell voltage- ramp protocol and delayed application of channel blockers. We postulate that transduction of some odors is caused by second messenger-mediated modulation of the resting membrane conductance (as opposed to a specialized generator conductance) in the cilia or apical region of the dendrite, and show how this could alter the firing frequency of olfactory neurons.