Modulation of Potassium-Evoked [³H]Dopamine Release from Rat Striatal Slices by Voltage-Activated Calcium Channel Ligands: Effects of ω-Conotoxin-MVIIC

Author： Dobrev Dobromir Andreas Klaus

Publisher： Springer Publishing Company

ISSN： 0364-3190

Source： Neurochemical Research, Vol.22, Iss.9, 1997-09, pp. : 1085-1093

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Abstract

We examined the involvement of voltage-activated Ca²⁺ channels (VACCs) on K⁺(50 mM)-evoked [³H]dopamine ([³H]DA) release from superfused rat striatal slices. Neither nifedipine nor nitrendipine modified K⁺-evoked [³H]DA release, indicating that L-type VACCs are not involved. K⁺-evoked [³H]DA release was partially inhibited by ω-CTx-GVIA and ω-Aga-IVA, and was abolished by 3 μM ω-CTx-MVIIC (IC50 ∼128 nM), suggesting the involvement of N-, P-, or Q-type VACCs, respectively. Moreover, even subnanomolar concentrations of ω-CTx-MVIIC (0.1–0.5 nM) inhibited K⁺-evoked [³H]DA release by ∼25%, suggesting the possible involvement of a still not classified (perhaps O-type?) Ca²⁺ channel subtype. The effects of ω-CTx-MVIIC (10–100 nM) and ω-CTx-GVIA (1 μM) were additive, suggesting that low nanomolar concentrations of ω-CTx-MVIIC does not interact with N-type VACCs. In conclusion, the K⁺-evoked [³H]DA release from rat striatal slices is mediated by entry of Ca²⁺ through ω-CTx-GVIA sensitive (N-type) as well as through ω-Aga-IVA (P-type) and ω-CTx-MVIIC (probably Q-type) sensitive VACCs.