Fluoxetine inhibits ATP-induced [Ca(2+)](i) increase in PC12 cells by inhibiting both extracellular Ca(2+) influx and Ca(2+) release from intracellular stores.
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 microM) for 2 min induced increases in intracellular free Ca(2+) concentrations ([Ca(2+)](i)). Treatment with fluoxetine (100 nM to 30 microM) for 5 min inhibited the ATP-induced [Ca(2+)](i) increases in a concentration-dependent manner (IC(50) = 1.85 microM). Treatment with fluoxetine (1.85 microM) for 5 min significantly inhibited the ATP-induced responses following the removal of extracellular Ca(2+) or depletion of intracellular Ca(2+) stores. Whereas treatment for 10 min with nimodipine (1 microM) significantly inhibited the ATP-induced [Ca(2+)](i) increase, treatment with fluoxetine further inhibited the ATP-induced response. Treatment with fluoxetine significantly inhibited [Ca(2+)](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 [Ca(2+)](i) increases in PC12 cells by inhibiting both the influx of extracellular Ca(2+) and the release of Ca(2+) from intracellular stores without affecting IPs formation.
Kim
Hee Jung
HJ
Department of Physiology, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Socho-gu, Seoul 137-701, South Korea.
Choi
Jin Sung
JS
Lee
Yeo-Min
YM
Shim
Eun Young
EY
Hong
Sun Hwa
SH
Kim
Myung-Jun
MJ
Min
Do Sik
DS
Rhie
Duck-Joo
DJ
Kim
Myung-Suk
MS
Jo
Yang-Hyeok
YH
Hahn
Sang June
SJ
Yoon
Shin Hee
SH
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D005473:Fluoxetine / Q000494:pharmacology*; D007294:Inositol / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009553:Nimodipine / Q000494:pharmacology; D016716:PC12 Cells / Q000187:drug effects*; D018408:Patch-Clamp Techniques / Q000379:methods; D051381:Rats; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology*; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors; D014316:Tritium / Q000378:metabolism
D000255:Adenosine Triphosphate; D002118:Calcium; D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D005473:Fluoxetine; D007294:Inositol; D009553:Nimodipine; D017367:Selective Serotonin Reuptake Inhibitors; D019284:Thapsigargin; D014316:Tritium