Nguyen Trung V, Matsuyama Hayato, Baell Jonathan, Hunne Billie, Fowler Christopher J, Smith Julia E, Nurgali Kulmira, Furness John B
Department of Anatomy and Cell Biology, University of Melbourne, Parkville, VIC 3010, Australia.
J Neurophysiol. 2007 Mar;97(3):2024-31. doi: 10.1152/jn.00935.2006. Epub 2007 Jan 17.
The late afterhyperpolarizing potential (AHP) that follows the action potential in intrinsic primary afferent neurons of the gastrointestinal tract has a profound influence on their firing patterns. There has been uncertainty about the identity of the channels that carry the late AHP current, especially in guinea pigs, where the majority of the physiological studies have been made. In the present work, the late AHP was recorded with intracellular microelectrodes from myenteric neurons in the guinea pig small intestine. mRNA was extracted from the ganglia to determine the identity of the guinea pig intermediate conductance potassium (I(K)) channel gene transcript. The late AHP was inhibited by two blockers of I(K) channels, TRAM34 (0.1-1 microM) and clotrimazole (10 microM), and was enhanced by the potentiator of the opening of these channels, DC-EBIO (100 nM). Action potential characteristics were unchanged by TRAM34 or DC-EBIO. The full sequence of the gene transcript and the deduced amino acid sequence were determined from extracts including myenteric ganglia and from bladder urothelium, which is a rich source of I(K) channel mRNA. This showed that the guinea pig sequence has a high degree of homology with other mammalian sequences but that the guinea pig channel lacks a phosphorylation site that was thought to be critical for channel regulation. It is concluded that the channels that carry the current of the late afterhyperpolarizing potential in guinea pig enteric neurons are I(K) channels.
胃肠道内在初级传入神经元动作电位之后的迟后超极化电位（AHP）对其放电模式有深远影响。关于携带迟后AHP电流的通道的身份一直存在不确定性，尤其是在豚鼠中，大多数生理学研究都是在豚鼠身上进行的。在本研究中，用细胞内微电极记录了豚鼠小肠肌间神经元的迟后AHP。从神经节中提取mRNA，以确定豚鼠中电导钾（I(K)）通道基因转录本的身份。迟后AHP受到两种I(K)通道阻滞剂TRAM34（0.1 - 1微摩尔）和克霉唑（10微摩尔）的抑制，并被这些通道开放的增强剂DC - EBIO（100纳摩尔）增强。TRAM34或DC - EBIO对动作电位特征没有影响。从包括肌间神经节的提取物以及膀胱尿路上皮（I(K)通道mRNA的丰富来源）中确定了基因转录本的完整序列和推导的氨基酸序列。这表明豚鼠序列与其他哺乳动物序列具有高度同源性，但豚鼠通道缺乏一个被认为对通道调节至关重要的磷酸化位点。得出的结论是，豚鼠肠神经元中携带迟后超极化电位电流的通道是I(K)通道。
