TIME COURSE OF THE MEMBRANE CURRENT UNDERLYING SENSORY TRANSDUCTION IN SALAMANDER OLFACTORY RECEPTOR NEURONS
TIME COURSE OF THE MEMBRANE CURRENT UNDERLYING SENSORY TRANSDUCTION IN SALAMANDER OLFACTORY RECEPTOR NEURONS
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DOI：
10.1113/jphysiol.1990.sp018286
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发表时间：
1990-11-01
影响因子：
5.5
通讯作者：
WERBLIN, FS
中科院分区：
文献类型：
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作者：
FIRESTEIN, S;SHEPHERD, GM;WERBLIN, FS
1.用全细胞膜片钳技术分析了新鲜分离的嗅觉受体神经元的气味诱发电流。气味溶液的短暂脉冲（35 - 50 ms）和步骤（100 ms-5 s）通过从附近的微量移液管的压力喷射来递送。2.指向细胞的气味溶液的脉冲诱导50 - 750 pA的向内去极化电流，导致动作电位的产生。该电流的I-V关系在-60-+20 mV范围内呈线性，并显示出+5 mV的反转电位。电流的大小随着刺激强度的增加，对于给定的脉冲持续时间，在大约十年的浓度变化。3.气味溶液的脉冲局部传递到纤毛引起了很大的反应，但那些直接对索马没有。相反，在纤毛处的K+溶液脉冲不能引起任何反应，而那些针对树突和索马的脉冲引起向内的钳电流。这提供了气味敏感性主要定位于纤毛和可能的远端树突的直接证据。4.在气味溶液到达细胞后，气味引发电流以150 - 600 ms的长潜伏期激活。这种潜伏期，以及时间到峰值和上升的半时间，是相对独立的刺激浓度，在整个浓度范围内的刺激灵敏度变化小于25%。这些观察结果是一致的第二信使系统在嗅觉转导的参与。5.由于短暂的刺激在气味响应电流达到峰值之前就扩散掉了，因此气味响应的峰值和衰减发生在没有明显气味刺激的情况下。电流衰减的时间过程通过具有时间常数的单指数拟合，该时间常数是浓度依赖性的，在0.8至1.3 s之间变化。6.对于更长的刺激呈现步骤，高达1秒，响应电流的大小成为脉冲的持续时间以及刺激浓度的函数，这表明转导过程涉及整合步骤。这与气味引起的电流是许多较小的单一事件的总和的结果的想法一致。根据对弱刺激的反应，计算出700 - 1000 ms的积分期。7.在维持刺激呈现的延长步骤（> 5s）期间，气味引起的电流是瞬时的。在不到1秒内达到峰值后，电流保持在该水平或接近该水平另外1 - 2秒，然后以4 - 6秒的时间常数指数衰减。在约40%的细胞中，衰减到约30%的峰值电流的强直水平。
1. Odour elicited currents in freshly isolated olfactory receptor neurones were analysed using the whole-cell patch-clamp technique. Brief pulses (35-50 ms) and steps (100 ms-5 s) of odour solution were delivered by pressure ejection from a nearby micropipette. 2. Pulses of odour solution directed at the cell induced an inward depolarizing current of 50-750 pA leading to the generation of action potentials. The I-V relation for this current was linear over the range -60-+20 mV and showed a reversal potential of +5 mV. The magnitude of the current increased with stimulus strength, for a given pulse duration, over approximately one decade of concentration change. 3. Pulses of odour solution focally delivered to the cilia elicited a large response, but those directed toward the soma did not. Conversely pulses of K+ solution at the cilia failed to evoke any response while those directed at the dendrite and soma elicited an inward clamp current. This provides direct evidence that odour sensitivity is localized mainly to the cilia and possibly the distal dendrite. 4. The odour elicited current activated with a long latency of 150-600 ms after the odour solution arrived at the cell. This latency, as well as the time-to-peak and the rise half-time, were relatively independent of stimulus concentration, changing less than 25% over the entire concentration range of stimulus sensitivity. These observations are consistent with the participation of a second messenger system in olfactory transduction. 5. For brief stimulus diffused away before the odour response current reached its peak value, so that the peak and decay of the odour response occurred in the absence of significant odour sitmulus. The time course of the current decay was fitted by a single exponential with a time constant that was concentration dependent, varying from 0.8 to 1.3 s. 6. For longer steps of stimulus presentation, up to 1 s, the magnitude of the response current became a function of the duration of the pulse as well as the stimulus concentration, indicating that the transduction process involved an integrating step. This is consistent with the idea that the odour elicited current is the result of the summation of many smaller unitary events. From responses to weak stimulation an integration period of 700-1000 ms was calculated. 7. During prolonged steps of maintained stimulus presentation (> 5 s) the odour elicited current was transient. After reaching a peak in less than 1 s than current remained at or near this level for an additional 1-2 s and then decayed exponentially with a time constant of 4-6 s. In about 40% of the cells the decay was to a tonic level of about 30% of the peak current.