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Evidence for a dihydropyridine-sensitive and conotoxin-insensitive release of noradrenaline and uptake of calcium in adrenal chromaffin cells

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  • P J OWEN
  • D B MARRIOTT
  • M R BOARDER
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<mark>Journal publication date</mark>05/1989
<mark>Journal</mark>British Journal of Pharmacology
Issue number1
Volume97
Number of pages6
Pages (from-to)133-138
Publication StatusPublished
<mark>Original language</mark>English

Abstract

1
It has been suggested that neuronal voltage-sensitive calcium channels (VSCC) may be divided into dihydropyridine (DHP)-sensitive (L) and DHP-insensitive (N and T), and that both the L and the N type channels are attenuated by the peptide blocker ω-conotoxin. Here the effects of ω-conotoxin on release of noradrenaline and uptake of calcium in bovine adrenal chromaffin cells were investigated.
2
Release of noradrenaline in response to 25 mm K+, 65 mm K+, 10 nm bradykinin or 10 μm prostaglandin E1 was not affected by ω-conotoxin in the range 10 nm-1 μm.
3
45Ca2+ uptake stimulated by high K+ and prostaglandin was attenuated by 1 μm nitrendipine and enhanced by 1 μm Bay K 8644; these calcium fluxes were not modified by 20 nm ω-conotoxin.
4
With superfused rat brain striatal slices in the same medium as the above cell studies, release of dopamine in response to 25 mm K+ was attenuated by 20 nm ω-conotoxin.
5
These results show that in these neurone-like cells, release may be effected by calcium influx through DHP-sensitive but ω-conotoxin-insensitive VSCC, a result inconsistent with the suggestion that ω-conotoxin blocks both L-type and N-type neuronal calcium channels.