title: Bimodal modulation of store-operated Ca2+channels by clozapine in astrocytes.
abstract: Clozapine (Clz) and olanzapine (Olz) are second generation (atypical) antipsychotics, used widely for treating schizophrenia and bipolar disorder. These drugs share multiple sites of actions, however their mechanisms remain incompletely understood. Here, we analyzed the effects of these drugs on primary cultures of rat cortical astrocytes and C6 glioma cells using fura-2-based Ca2+imaging. C6 cells, but not cortical astrocytes, express the serotonin 2A receptor subtype, which couples to phospholipase C. Clz (1μM) significantly blocked serotonin-induced Ca2+transients in C6 cells, consistent with known antagonistic actions of Clz. Interestingly, at higher concentrations (>10μM), Clz but not Olz increased intracellular Ca2+concentrations in both cortical astrocytes and C6 cells. This Clz-induced Ca2+increase was concentration-dependent and completely blocked by removal of extracellular Ca2+using ethylene glycol tetraacetic acid (EGTA). Furthermore, 2-aminoethyl diphenylborinate or SKF-96365, blockers for store-operated Ca2+channels, significantly inhibited the Clz-induced Ca2+increase. Therefore, we analyzed the effects of Clz and Olz during Ca2+re-entry through store-operated Ca2+channels, which was maximized following depletion of internal Ca2+stores by thapsigargin and EGTA. The results demonstrated that Clz decreased Ca2+re-entry through store-operated Ca2+channels in cortical astrocytes and C6 cells whereas Olz failed to modulate the Ca2+re-entry. These results suggest Clz-specific bimodal actions via store-operated Ca2+channels in astrocytic cells. Since intracellular Ca2+homeostasis in astrocytes is an important determinant for neighboring synaptic signal transmission, our results may explain Clz-specific adverse effects or differential actions between Clz and Olz reported in the treatment of psychiatric disorders.
authors: Graduate School of Science and Engineering, University of Toyama, Toyama 930-8555, Japan. Electronic address: m1641308@ems.u-toyama.ac.jp.
authors: Yuzuki
authors: Y
authors: Kanda
authors: Graduate School of Science and Engineering, University of Toyama, Toyama 930-8555, Japan. Electronic address: m1541307@ems.u-toyama.ac.jp.
authors: Miho
authors: M
authors: Okada
authors: Graduate School of Science and Engineering, University of Toyama, Toyama 930-8555, Japan. Electronic address: m1541302@ems.u-toyama.ac.jp.
authors: Rina
authors: R
authors: Ikarashi
authors: Graduate School of Science and Engineering, University of Toyama, Toyama 930-8555, Japan. Electronic address: emorioka@sci.u-toyama.ac.jp.
authors: Eri
authors: E
authors: Morioka
authors: Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama 930-0194, Japan. Electronic address: kondot@med.u-toyama.ac.jp.
authors: Takashi
authors: T
authors: Kondo
authors: Graduate School of Science and Engineering, University of Toyama, Toyama 930-8555, Japan. Electronic address: msikeda@sci.u-toyama.ac.jp.
authors: Masayuki
authors: M
authors: Ikeda
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D014150:Antipsychotic Agents / Q000494:pharmacology*; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism; D001569:Benzodiazepines / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D003024:Clozapine / Q000494:pharmacology*; D000077152:Olanzapine; D061251:Primary Cell Culture; D017207:Rats, Sprague-Dawley; D044402:Receptor, Serotonin, 5-HT2A / Q000378:metabolism
chemical_list: D014150:Antipsychotic Agents; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D044402:Receptor, Serotonin, 5-HT2A; D001569:Benzodiazepines; D003024:Clozapine; D000077152:Olanzapine
keywords: Astrocytes; Clozapine; Cytosolic calcium; Olanzapine; Store-operated Ca(2+) entry