Ca2+ channels that activate Ca2+-dependent K+ currents in neostriatal neurons
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- 作者：Vilchis ; C. ; Bargas ; J. ; Ayala ; G.X. ; Galvá ; n ; E. ; Galarraga ; E.
- 关键词：calcium currents ; basal ganglia ; calcium-activated potassium currents ; neostriatum ; afterhyperpolarization ; firing pattern ; AHP ; afterhyperpolarizing potential or afterhyperpolarization ; 4-AP ; 4-aminopyridine ; BK ; &ldquo ; big conductance&rdquo ; or &ldquo ; m
- 刊名：Neuroscience
- 出版年：1999
- 出版时间：December, 1999
- 年：1999
- 卷：95
- 期：3
- 页码：745-752
- 全文大小：315 K
文摘
It is demonstrated that not all voltage-gated calcium channel types expressed in neostriatal projection neurons (L, N, P, Q and R) contribute equally to the activation of calcium-dependent potassium currents. Previous work made clear that different calcium channel types contribute with a similar amount of current to whole-cell calcium current in neostriatal neurons. It has also been shown that spiny neurons posses both “big” and “small” types of calcium-dependent potassium currents and that activation of such currents relies on calcium entry through voltage-gated calcium channels. In the present work it was investigated whether all calcium channel types equally activate calcium-dependent potassium currents. Thus, the action of organic calcium channel antagonists was investigated on the calcium-activated outward current. Transient potassium currents were reduced by 4-aminopyridine and sodium currents were blocked by tetrodotoxin. It was found that neither 30 nM ω-Agatoxin-TK, a blocker of P-type channels, nor 200 nM calciseptine or 5 μM nitrendipine, blockers of L-type channels, were able to significantly reduce the outward current. In contrast, 400 nM ω-Agatoxin-TK, which at this concentration is able to block Q-type channels, and 1 μM ω-Conotoxin GVIA, a blocker of N-type channels, both reduced outward current by about 50 % . These antagonists given together, or 500 nM ω-Conotoxin MVIIC, a blocker of N- and P/Q-type channels, reduced outward current by 70 % . In addition, the N- and P/Q-type channel blockers preferentially reduce the afterhyperpolarization recorded intracellularly.
The results show that calcium-dependent potassium channels in neostriatal neurons are preferentially activated by calcium entry through N- and Q-type channels in these conditions.