Division of Biology, California Institute of Technology, Pasadena, CA, USA.
J Neurophysiol. 2012 Sep;108(5):1318-34. doi: 10.1152/jn.00907.2011. Epub 2012 May 30.
Mammals rely on their acute olfactory sense for their survival. The most anterior olfactory subsystem in the nose, the Grueneberg ganglion (GG), plays a role in detecting alarm pheromone, cold, and urinary compounds. GG neurons respond homogeneously to these stimuli with increases in intracellular [Ca(2+)] or transcription of immediate-early genes. In this electrophysiological study, we used patch-clamp techniques to characterize the membrane properties of GG neurons. Our results offer evidence of functional heterogeneity in the GG. GG neurons fire spontaneously and independently in several stable patterns, including phasic and repetitive single-spike modes of discharge. Whole cell recordings demonstrated two distinct voltage-gated fast-inactivating Na(+) currents with different steady-state voltage dependencies and different sensitivities to tetrodotoxin. Hodgkin-Huxley simulations showed that these Na(+) currents confer dual mechanisms of action potential generation and contribute to different firing patterns. Additionally, GG neurons exhibited hyperpolarization-activated inward currents that modulated spontaneous firing in vitro. Thus, in GG neurons, the heterogeneity of firing patterns is linked to the unusual repertoire of ionic currents. The membrane properties described here will aid the interpretation of chemosensory function in the GG.
哺乳动物依靠敏锐的嗅觉来生存。鼻子中最靠前的嗅觉子系统——格鲁恩伯格神经节（GG）在探测警报信息素、寒冷和尿液化合物方面发挥作用。GG 神经元对这些刺激物的反应一致，表现为细胞内 [Ca(2+)]的增加或即刻早期基因的转录。在这项电生理研究中，我们使用膜片钳技术来描述 GG 神经元的膜特性。我们的结果为 GG 中的功能异质性提供了证据。GG 神经元以几种稳定的模式自主和独立地放电，包括相位和重复的单峰放电模式。全细胞记录显示存在两种不同的电压门控快速失活的 Na(+)电流，它们具有不同的稳态电压依赖性和对河豚毒素的不同敏感性。Hodgkin-Huxley 模拟表明，这些 Na(+)电流赋予动作电位产生的双重机制，并有助于不同的放电模式。此外，GG 神经元表现出超极化激活内向电流，在体外调节自发放电。因此，在 GG 神经元中，放电模式的异质性与离子电流的不寻常组成有关。本文描述的膜特性将有助于解释 GG 中的化学感觉功能。
