Fluoxetine, a widely used antidepressant, has additional effects, including the blocking of voltage-gated ion channels. We examined whether fluoxetine affects ATP-induced calcium signaling in PC12 cells using fura-2-based digital calcium imaging, an assay for [3H]-inositol phosphates (IPs) and whole-cell patch clamping. Treatment with ATP (100 μM) for 2 min induced increases in intracellular free Ca2+ concentrations ([Ca 2+]i). Treatment with fluoxetine (100 nM to 30 μM) for 5 min inhibited the ATP-induced [Ca2+]i increases in a concentration-dependent manner (IC50 = 1.85 μM). Treatment with fluoxetine (1.85 μM) for 5 min significantly inhibited the ATP-induced responses following the removal of extracellular Ca2+ or depletion of intracellular Ca2+ stores. Whereas treatment for 10 min with nimodipine (1 μM) significantly inhibited the ATP-induced [Ca 2+]i increase, treatment with fluoxetine further inhibited the ATP-induced response. Treatment with fluoxetine significantly inhibited [Ca2+]i increases induced by 50 mM K+. In addition, treatment with fluoxetine markedly inhibited ATP-induced inward currents in a concentration-dependent manner. However, treatment with fluoxetine did not inhibit ATP-induced [3H]-IPs formation. Therefore, we conclude that fluoxetine inhibits ATP-induced [Ca2+]i increases in PC12 cells by inhibiting both the influx of extracellular Ca 2+ and the release of Ca2+ from intracellular stores without affecting IPs formation.
Bibliographical noteFunding Information:
This work was supported by the Korea Science & Engineering Foundation (KOSEF) through the Cell Death Disease Research Center at the Catholic University of Korea (R13-2002-005-01002-0).
All Science Journal Classification (ASJC) codes
- Cellular and Molecular Neuroscience