Two different inward rectifier K+ channels are effectors for transmitter-induced slow excitation in brain neurons

被引:20
作者
Bajic, D
Koike, M
Albsoul-Younes, AM
Nakajima, S
Nakajima, Y
机构
[1] Univ Illinois, Dept Anat & Cell Biol, Chicago, IL 60612 USA
[2] Univ Illinois, Dept Pharmacol, Chicago, IL 60612 USA
关键词
D O I
10.1073/pnas.222379999
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
Substance P (SP) excites large neurons of the nucleus basalis (NB) by inhibiting an inward rectifier K+ channel (Kir). The properties of the Kir in NB (KirNB) in comparison with the G protein-coupled Kir (GIRK) were investigated. Single-channel recordings with the cell-attached mode showed constitutively active KirNB channels, which were inhibited by SP. When the recording method was changed from the on-cell to the inside-out mode, the channel activity of KirNB remained intact with its constitutive activity unaltered. Application of Gbeta(1gamma2) to inside-out patches induced activity of a second type of Kir (GIRK). Application of Gbeta(1gamma2), however, did not change the KirNB activity. Sequestering Gbeta(1gamma2) with Galpha(i2) abolished the GIRK activity, whereas the KirNB activity was not affected. The mean open time of KirNB channels (1.1 ms) was almost the same as that of GIRKs. The unitary conductance of KirNB was 23 pS (1155 mM [K+](o)), whereas that of the GIRK was larger (32-39 pS). The results indicate that KirNB is different from GIRKs and from any of the classical Kirs (IRKs). Whole-cell current recordings revealed that application of muscarine to NB neurons induced a GIRK current, and this GIRK current was also inhibited by SP. Thus, SP inhibits both KirNB and GIRKs. We conclude that the excitatory transmitter SP has two types of Kirs as its effectors: the constitutively active, Gbetagamma-independent KirNB channel and the Gbetagamma-dependent GIRK.
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页码:14494 / 14499
页数:6
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