Title : Voltage-sensitive Ca2+ channels involved in nicotinic receptor-mediated [3H]dopamine release from rat striatal synaptosomes - Soliakov_1996_J.Neurochem_67_163 |
Author(s) : Soliakov L , Wonnacott S |
Ref : Journal of Neurochemistry , 67 :163 , 1996 |
Abstract :
The potent nicotinic agonist anatoxin-a elicits mecamylamine-sensitive [3H]dopamine release from striatal synaptosomes, and this action is both Na+ and Ca2+ dependent and is blocked by Cd2+. This suggests that stimulation of presynaptic nicotinic receptors results in Na+ influx and local depolarisation that activates voltage-sensitive Ca2+ channels, which in turn provide the Ca2+ for exocytosis. Here we have investigated the subtypes of Ca2+ channels implicated in this mechanism. [3H]-Dopamine release evoked by anatoxin-a (1 microM) was partially blocked by 20 microM nifedipine, whereas KCl-evoked release was insensitive to the dihydropyridine. However, a 86Rb+ efflux assay of nicotinic receptor function suggested that nifedipine has a direct effect on the receptor, discrediting the involvement of L-type channels. The N-type Ca2+ channel blocker omega-conotoxin GVIA (1 microM) blocked anatoxin-a-evoked [3H]dopamine release by 60% but had no significant effect on 86Rb+ efflux; release evoked by both 15 and 25 mM KCl was inhibited by only 30%. The P-type channel blocker omega-agatoxin IVA (90 nM) also inhibited KCl-evoked release by approximately 30%, whereas anatoxin-a-evoked release was insensitive. The Q-type channel blocker omega-conotoxin MVIIC (1 microM) had no effect on either stimulus. These results suggest that presynaptic nicotinic receptors on striatal nerve terminals promote [3H]dopamine release by activation of N-type Ca2+ channels. In contrast, KCl-evoked [3H]dopamine release appears to involve both N-type and P-type channels. |
PubMedSearch : Soliakov_1996_J.Neurochem_67_163 |
PubMedID: 8666987 |
Soliakov L, Wonnacott S (1996)
Voltage-sensitive Ca2+ channels involved in nicotinic receptor-mediated [3H]dopamine release from rat striatal synaptosomes
Journal of Neurochemistry
67 :163
Soliakov L, Wonnacott S (1996)
Journal of Neurochemistry
67 :163