L-type calcium channels mediate synchronized spontaneous Ca2+spikes in cultured cortical networks

We have detected synchronized spontaneous Ca
²⁺
spikes in cultured cortical networks in the presence of Mg
²⁺
. The synchronized spontaneous Ca
²⁺
spikes are synaptically driven, as it is blocked by tetrodotoxin (TTX), and by the glutamate receptor antagonist CNQX/APV. The oscillatory activity is not influenced by GABA
_A
receptor antagonist picrotoxin, suggesting that they entirely rely on glutamatergic neurotransmission. We have also found that these Ca
²⁺
spikes are dependent on an influx of extracellular Ca
²⁺
but are independent of mobilization of Ca
²⁺
from intracellular Ca
²⁺
stores. Ca
²⁺
entry occurred primarily through L-type voltage-gated calcium channels (VGCCs), since nifedipine completely blocked these Ca
²⁺
spikes