Involvement of intracellular calcium stores during oxygen/glucose deprivation in striatal large aspiny interneurons

Striatal large aspiny interneurons were recorded from a slice preparation u sing a combined electrophysiologic and microfluorometric approach. The role of intracellular Ca2+ stores was analyzed during combined oxygen/glucose d eprivation (OGD). Before addressing the role of the stores during energy de privation, the authors investigated their function under physiologic condit ions. Trains of depolarizing current pulses caused bursts of action potenti als coupled to transient increases in intracellular calcium concentration ( [Ca2+](i)). In the presence of cyclopiazonic acid (30 mu mol/L), a selectiv e inhibitor of the sarcoendoplasmic reticulum Ca2+ pumps, or when ryanodine receptors were directly blocked with ryanodine (20 mu mol/L), the [Ca2+](i ) transients were progressively smaller in amplitude, suggesting that [Ca2]; released from intracellular stores helps to maintain a critical level of [Ca2+], during physiologic firing activity. As the authors have recently r eported, brief exposure to combined OGD induced a membrane hyperpolarizatio n coupled to an increase in [Ca2+](i). In the presence of cyclopiazonic aci d or ryanodine, the hyperpolarization and the rise in [Ca2+](i) induced by OGD were consistently reduced. These data support the hypothesis that Ca2release from ryanodine-sensitive Ca2+ pools is involved not only in the pot entiation of the Ca2+ signals resulting from cell depolarization, but also in the amplification of the [Ca2+], rise and of the concurrent membrane hyp erpolarization observed in course of OGD in striatal large aspiny interneur ons.