ISSN:
1432-2013
Keywords:
Cerebellum
;
Potassium channels
;
Dihydropyridines
;
Mouse
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract In cultured cerebellar granule cells, we examined the effects of dihydropyridines (DHPs) on K+ currents, using the whole-cell recording configuration of the patch-clamp technique and on Ca2+-activated K+ channels (“maxi K+ channels”) using outside-out patches. We found that micromolar concentrations of nicardipine, nifedipine, (+) and (−) BAY K 8644, nitrendipine, nisoldipine and (−) nimodipine block 10–60% of macroscopic K+ currents. The most potent of these DHPs was nicardipine and the least potent, (−) BAY K 8644. (+) Nimodipine had no effect on this current. The inhibitory effects of nifedipine and nicardipine were not additive with those of 1 mM tetraethylammonium (TEA). Outside-out recordings of “maxi K+ channels” showed a main conductance of 200 pS (in 77% of the patches) and two subconductance states (in 23% of the patches). Neither nifedipine nor nicardipine affected the main conductance, but decreased the values of the subconductance levels. In 10% of these patches, nicardipine induced a flickering activity of the channel. These findings show that both Ca2+ and K+ channels have DHP-sensitive sites, suggesting similarity in electrostatic binding properties of these channels. Furthermore, cerebellar granule cells may express different subtypes of “maxi K+ channels” having different sensitivities to DHPs. These drugs may provide new tools for the molecular study of K+ channels.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00374310
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