Ca2+ channels that activate Ca2+-dependent K+ currents in neostriatal neurons

Neuroscience. 2000;95(3):745-52. doi: 10.1016/s0306-4522(99)00493-5.


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 possess 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 omega-Agatoxin-TK, a blocker of P-type channels, nor 200 nM calciseptine or 5 microM nitrendipine, blockers of L-type channels, were able to significantly reduce the outward current. In contrast, 400 nM omega-Agatoxin-TK, which at this concentration is able to block Q-type channels, and 1 microM omega-Conotoxin GVIA, a blocker of N-type channels, both reduced outward current by about 50%. These antagonists given together, or 500 nM omega-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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / physiology*
  • Calcium Channel Blockers / pharmacology
  • Calcium Channels / physiology*
  • Electric Conductivity
  • Electrophysiology
  • Neostriatum / cytology
  • Neostriatum / metabolism*
  • Neurons / metabolism*
  • Potassium / physiology*
  • Rats
  • Rats, Wistar


  • Calcium Channel Blockers
  • Calcium Channels
  • Potassium
  • Calcium