Trombley P Q, Westbrook G L
Department of Biology, University of Oregon, Portland.
J Neurosci. 1991 Feb;11(2):435-44. doi: 10.1523/JNEUROSCI.11-02-00435.1991.
Whole-cell recording techniques were used to characterize voltage-gated membrane currents in neonatal rat olfactory receptor neurons (ORNs) in cell culture. Mature ORNs were identified in culture by their characteristic bipolar morphology, by retrograde labeling techniques, and by olfactory marker protein (OMP) immunoreactivity. ORNs did not have spontaneous activity, but fired action potentials to depolarizing current pulses. Action potentials were blocked by tetrodotoxin (TTX), which contrasts with the TTX-resistant action potentials in salamander olfactory receptor cells (e.g., Firestein and Werblin, 1987). Prolonged, suprathreshold current pulses evoked only a single action potential; however, repetitive firing up to 35 Hz could be elicited by a series of brief depolarizing pulses. Under voltage clamp, the TTX-sensitive sodium current had activation and inactivation properties similar to other excitable cells. In TTX and 20 mM barium, sustained inward current were evoked by voltage steps positive to -30 mV. This current was blocked by Cd (100 microM) and by nifedipine (IC50 = 368 nM) consistent with L-type calcium channels in other neurons. No T-type calcium current was observed. Voltage steps positive to -20 mV also evoked an outward current that did not inactivate during 100-msec depolarizations. Tail current analysis of this current was consistent with a selective potassium conductance. The outward current was blocked by external tetraethylammonium but was unaffected by Cd or 4-aminopyridine (4-AP) or by removal of external calcium. A transient outward current was not observed. The 3 voltage-dependent conductances in cultured rat ORNs appear to be sufficient for 2 essential functions: action potential generation and transmitter release. As a single odorant-activated channel can trigger an action potential (e.g., Lynch and Barry, 1989), the repetitive firing seen with brief depolarizing pulses suggests that ORNs do not integrate sensory input, but rather act as high-fidelity relays such that each opening of an odorant-activated channel reaches the olfactory bulb glomeruli as an action potential.
全细胞记录技术用于在细胞培养中表征新生大鼠嗅觉受体神经元（ORN）的电压门控膜电流。通过其特征性的双极形态、逆行标记技术和嗅觉标记蛋白（OMP）免疫反应性在培养物中鉴定出成熟的ORN。ORN没有自发活动，但对去极化电流脉冲产生动作电位。动作电位被河豚毒素（TTX）阻断，这与蝾螈嗅觉受体细胞中对TTX有抗性的动作电位形成对比（例如，Firestein和Werblin，1987）。长时间的阈上电流脉冲仅诱发单个动作电位；然而，一系列短暂的去极化脉冲可诱发高达35Hz的重复放电。在电压钳制下，TTX敏感的钠电流具有与其他可兴奋细胞相似的激活和失活特性。在TTX和20mM钡中，向正于-30mV的电压阶跃诱发持续的内向电流。该电流被镉（100μM）和硝苯地平（IC50 = 368nM）阻断，这与其他神经元中的L型钙通道一致。未观察到T型钙电流。向正于-20mV的电压阶跃也诱发外向电流，该电流在100毫秒去极化期间不会失活。对该电流的尾电流分析与选择性钾电导一致。外向电流被细胞外四乙铵阻断，但不受镉、4-氨基吡啶（4-AP）或去除细胞外钙的影响。未观察到瞬时外向电流。培养的大鼠ORN中的三种电压依赖性电导似乎足以实现两种基本功能：动作电位的产生和递质释放。由于单个气味激活通道可触发动作电位（例如，Lynch和Barry，1989），短暂去极化脉冲所见的重复放电表明ORN不整合感觉输入，而是充当高保真中继，使得气味激活通道的每次开放都作为动作电位到达嗅球小球。
