Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA.
J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2011 Apr;197(4):339-49. doi: 10.1007/s00359-010-0618-1. Epub 2011 Jan 21.
Odorant stimulation of olfactory receptor neurons (ORNs) leads to the activation of a Ca(2+) permeable cyclic nucleotide-gated (CNG) channel followed by opening of an excitatory Ca(2+)-activated Cl(-) channel, which carries about 70% of the odorant-induced receptor current. This requires ORNs to have a Cl(-) above the electrochemical equilibrium to render this anionic current excitatory. In mammalian ORNs, the Na(+)-K(+)-2Cl(-) co-transporter 1 (NKCC1) has been characterized as the principal mechanism by which these neurons actively accumulate Cl(-). To determine if NKCC activity is needed in amphibian olfactory transduction, and to characterize its cellular location, we used the suction pipette technique to record from Rana pipiens ORNs. Application of bumetanide, an NKCC blocker, produced a 50% decrease of the odorant-induced current. Similar effects were observed when Cl(-) was decreased by bathing ORNs in low Cl(-) solution. Both manipulations reduced only the Cl(-) component of the current. Application of bumetanide only to the ORN cell body and not to the cilia decreased the current by again about 50%. The results show that NKCC is required for amphibian olfactory transduction, and suggest that the co-transporter is located basolaterally at the cell body although its presence at the cilia could not be discarded.
气味刺激嗅觉受体神经元（ORNs）会导致钙通透性环核苷酸门控（CNG）通道的激活，随后是兴奋性钙激活氯离子通道的开放，该通道携带约 70%的气味诱导受体电流。这要求 ORNs 的 Cl(-) 高于电化学平衡，以使这种阴离子电流具有兴奋性。在哺乳动物 ORNs 中，Na(+)-K(+)-2Cl(-)共转运蛋白 1（NKCC1）已被确定为这些神经元主动积累 Cl(-)的主要机制。为了确定 NKCC 活性是否在两栖动物嗅觉转导中是必需的，并对其细胞位置进行表征，我们使用吸液管技术从牛蛙 ORNs 中进行记录。应用 NKCC 阻断剂布美他尼会导致气味诱导电流减少 50%。当用低 Cl(-)溶液孵育 ORNs 来降低 Cl(-) 时，也观察到类似的效果。这两种操作都仅减少了电流的 Cl(-)成分。仅将布美他尼应用于 ORN 细胞体而不是纤毛，电流又减少了约 50%。结果表明，NKCC 是两栖动物嗅觉转导所必需的，并且表明共转运蛋白位于细胞体的基底外侧，尽管不能排除其存在于纤毛中。
