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

Brain Research
Publication Date
DOI: 10.1016/0006-8993(93)90989-z
  • Flunarizine
  • Glutamate Release
  • Ca2+Channel
  • Na+Channel
  • Veratridine
  • Ouabain
  • Tetrodotoxin


Abstract Flunarizine, an established Ca 2+ 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 Ca 2+, 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 Ca 2+, [Ca 2+] 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 [Ca 2+] 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 Ca 2+-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 Ca 2+ channels and tetrodotoxin-sensitive Na + channels.

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