Elsevier

Brain Research

Volume 606, Issue 2, 26 March 1993, Pages 227-236
Brain Research

Flunarizine inhibits both calcium-dependent and -independent release of glutamate from synaptosomes and cultured neurones

https://doi.org/10.1016/0006-8993(93)90989-ZGet rights and content

Abstract

Flunarizine, an established Ca2+ channel antagonist, blocks both exocytotic and non-exocytotic glutamate release from mammalian cultured cerebellar granule cells and isolated presynaptic nerve endings (synaptosomes) prepared from two distinct areas of the mammalian brain. This blockade of release displays the same flunarizine concentration dependency in synaptosomes in the presence or absence of Ca2+, with total inhibition at a concentration of 10 μM. In cultured neurones, a selective effect on the L-channel-coupled component of the KCI-evoked rise in intracellular Ca2+, [Ca2+]c, can be demonstrated between flunarizine concentrations of 100 nM and 10 μM, while at concentrations above 10 μM, the remaining residual and transient components are affected. In synaptosomes, flunarizine blocks the KCI-evoked elevation in [Ca2+]c in a concentration-dependent manner. Additionally, 10 μM flunarizine directly antagonises ouabain-induced tetrodotoxin (TTX)-sensitive Na+ influx, glutamate, aspartate and GABA release from synaptosomes, whilst inhibiting veratridine-induced Ca2+-independent TTX-sensitive Na+ influx and glutamate release at 15 μM and 10 μM in cells and synaptosomes, respectively. In both cultured neurones and synaptosomes, the ability of flunarizine to block both neurotransmitter and cytoplasmic glutamate release is due to a direct antagonism of both voltage dependent Ca2+ channels and tetrodotoxin-sensitive Na+ channels.

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