Responses to prolonged odour stimulation in frog olfactory receptor cells
Responses to prolonged odour stimulation in frog olfactory receptor cells
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DOI：
10.1111/j.1469-7793.2001.t01-1-00179.x
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发表时间：
2001-07-01
影响因子：
5.5
通讯作者：
Matthews, HR
中科院分区：
文献类型：
--
作者：
Reisert, J;Matthews, HR
1.采用吸管法记录蛙嗅感受器细胞在长时间气味刺激下的感受器电流和峰电位反应.大多数（70%）细胞显示出“振荡”反应，包括伴随受体电流定期增加的重复尖峰脉冲。这种振荡的周期在不同细胞中变化从3.5到12 a。其余的细胞要么在刺激开始时以“瞬时”尖峰脉冲的爆发（10%）作出反应，要么在整个气味刺激过程中以“持续”放电（20%）作出反应。在振荡反应的细胞中，钙激活的Cl-通道阻滞剂尼氟灭酸仅略微延长振荡周期，尽管受体电流降低了3.8倍。在外部Cl-浓度的3倍减少近一倍的受体电流，但对振荡周期的影响不大。这些结果表明，这些振荡反应背后的受体电流大部分是由Ca 2+激活的Cl-电导携带的，这表明细胞内Ca 2+浓度也是振荡的.在振荡反应的细胞中，振荡周期延长1.5倍，当在低Na+溶液中刺激时，该溶液旨在使Na+-Ca 2+交换丧失能力，而不管Na+是否被渗透的Li+或不渗透的胆碱所取代。振荡周期对外界Na+的依赖性表明它可能受Na+-Ca 2+交换的Ca 2+挤出动力学的控制.暴露于膜可渗透的环核苷酸类似物CPT-cAMP引起了持续的，而不是振荡反应，即使在细胞的振荡反应气味。CPT-cAMP不能引起振荡反应，表明cAMP浓度也可能振荡。穿孔贴片记录显示，振荡反应只能诱发时，膜电位是自由改变，但不是当它被夹在附近的静息电位。由于Ca 2+激活的Cl-电流的实质性变化，因此气味诱导的去极化，对振荡周期的影响很小，因此建议膜电位的变化在这些振荡反应中仅起允许的作用。这些结果被解释在耦合振荡的Ca 2+和环核苷酸浓度内的嗅觉纤毛在长时间的气味刺激。
1. The suction pipette technique was used to record receptor current and spiking responses from isolated frog olfactory receptor cells during prolonged odour stimuli.2. The majority (70 %) of cells displayed 'oscillatory' responses, consisting of repeated bursts of spikes accompanied by regular increases in receptor current. The period of this oscillation varied from 3.5 to 12 a in different cells. The remaining cells responded either with a 'transient' burst of spikes at the onset of stimulation (10 %), or by 'sustained' firing throughout the odour stimulus (20 %).3. In cells with oscillatory responses, the Ca2+-activated Cl- channel blocker niflumic acid prolonged the period of oscillation only slightly, despite a 3.8-fold decrease in the receptor current. A 3-fold reduction in the external Cl- concentration nearly doubled the receptor current, but had little effect on the oscillation period. These results imply that the majority of the receptor current underlying these oscillatory responses is carried by the Ca2+-activated Cl- conductance, suggesting that the intracellular Ca2+ concentration oscillates also.4. In cells with oscillatory responses, the period of oscillation was prolonged 1.5-fold when stimulated in a low-Na+ solution designed to incapacitate Na+-Ca2+ exchange, irrespective of whether Na+ was replaced by permeant Li+ or impermeant choline. The dependence of the oscillation period upon external Na+ suggests that it may be governed by the dynamics of Ca2+ extrusion via Na+-Ca2+ exchange.5. Exposure to the membrane-permeable cyclic nucleotide analogue CPT-cAMP evoked a sustained rather than an oscillatory response even in cells with oscillatory responses to odour. The inability of CPT-cAMP to evoke an oscillatory response suggests that the cAMP concentration is likely to oscillate also.6. Perforated-patch recordings revealed that oscillatory responses could only be evoked when the membrane potential was free to change, but not when it was clamped near the resting potential. Since substantial changes in Ca2+-activated Cl- current, and hence odour-induced depolarisation, had little effect upon the period of oscillation, changes in membrane potential are suggested to play only a permissive role in these oscillatory responses.7. These results are interpreted in terms of the coupled oscillation of Ca2+ and cyclic nucleotide concentrations within the olfactory cilia during prolonged odour stimulation.