Clozapine, but not haloperidol, enhances glial d‐serine and L‐glutamate release in rat frontal cortex and primary cultured astrocytes

Abstract

BACKGROUND AND PURPOSEDeficient transmission at the glutamate NMDA receptor is considered a key component of the pathophysiology of schizophrenia. However, the effects of antipsychotic drugs on the release of the endogenous NMDA receptor partial agonist, D-serine, remain to be clarified. EXPERIMENTAL APPROACHWe determined the interaction between antipsychotic drugs (clozapine and haloperidol) and transmission-modulating toxins (tetanus toxin, fluorocitrate, tetrodotoxin) on the release of L-glutamate and D-serine in the medial prefrontal cortex (mPFC) of freely moving rats, using microdialysis, and primary cultures of astrocytes using extreme high-pressure liquid chromatography. KEY RESULTSRelease of L-glutamate and D-serine in the mPFC and in cultured astrocytes was inhibited by tetanus toxin (a synaptobrevin inhibitor) and fluorocitrate (a glial toxin), whereas tetrodotoxin (a voltage-sensitive Na + blocker) inhibited depolarization-induced L-glutamate release in the mPFC without affecting that of D-serine. Clozapine (1 and 5 mg·kg -1 ), but not haloperidol (0.5 and 1 mg·kg -1 ), dose-dependently increased L-glutamate and D-serine release from both astrocytes and mPFC. Clozapine-induced release of L-glutamate and D-serine was also reduced by tetanus toxin and fluorocitrate. Tetrodotoxin reduced clozapine-induced mPFC L-glutamate release but not that of D-serine. Clozapine-induced L-glutamate release preceded clozapine-induced D-serine release. MK-801 (a NMDA receptor antagonist) inhibited the delayed clozapine-induced L-glutamate release without affecting that of D-serine. CONCLUSIONS AND IMPLICATIONSClozapine predominantly activated glial exocytosis of D-serine, and this clozapine-induced D-serine release subsequently enhances neuronal L-glutamate release via NMDA receptor activation. The enhanced D-serine associated glial transmission seems a novel mechanism of action of clozapine but not haloperidol.

ONO‐2506 inhibits spike–wave discharges in a genetic animal model without affecting traditional convulsive tests via gliotransmission regulation

“…) for 24 h (pre-incubation with TeNT: this process was omitted in other experiments) Mothet et al, 2005;Tanahashi et al, 2012). To study the effects of fluorocitrate (FLC) on glial transmitters release, astrocytes were incubated in a fresh culture medium containing 1 mM FLC for 8 h (pre-incubation with FLC: this process was omitted in other experiments) (Tanahashi et al, 2012).…”

“…To study the effects of fluorocitrate (FLC) on glial transmitters release, astrocytes were incubated in a fresh culture medium containing 1 mM FLC for 8 h (pre-incubation with FLC: this process was omitted in other experiments) (Tanahashi et al, 2012).…”

“…The medium was removed and discarded, and the flask contents were harvested and reseeded to yield double the original number of flasks. Astrocytes were removed from flasks by trypsinization and seeded onto translucent PET membrane (8 mm) 24-well plates (BD) at a density of 10 5 cells cm -2 for experiments on DIV21 (Tanahashi et al, 2012).…”

“…Furthermore, the present study also determined the effects of ONO-2506 on the release of L-glutamate, D-serine, GABA and kynurenic acid, in the medial prefrontal cortex (mPFC) of freely moving rats and in primary cultured astrocytes by extreme liquid chromatography (xLC) (Yamamura et al, 2009b;Tanahashi et al, 2012) and HPLC equipped with nanocarbon film electrode detection (NCE-HPLC) (Kato et al, 2011).…”

Role of astrocytes in alterations of glutamatergic neurotransmission in schizophrenia

“…Однако, по их данным, уровень D-серина достоверно по-вышался после приема курса антипсихотических препа-ратов. Показано, что клозапин (но не галоперидол) уси-ливает выделение D-серина астроцитами как в мозге крыс, так и клеточной культуре [59]. Кроме того, типич-ные и атипичные нейролептики способны также пода-влять активность глиальных транспортеров глицина in vitro, что приводит к увеличению перисинаптической кон-центрации этой аминокислоты [60].…”