Stimulation of Phosphoinositide Hydrolysis by Serotonin in C6 Glioma Cells

Ananth, Uma; Leli, Ubaldo; Hauser, George

doi:10.1111/j.1471-4159.1987.tb13156.x

Cited by 58 publications

(27 citation statements)

References 47 publications

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“…On the basis of its affinity for the receptors in ligand binding studies, 1 M SB 200646 would be expected to block both the 5-HT 2B and the 5-HT 2C receptors, with receptor occupancies of 97% and 88%, respectively, but not the 5-HT 2A receptor (14% receptor occupancy; Kennet, 1993). These findings are consistent with previous reports that demonstrate the expression of 5-HT 2A receptors by C6 glioma cells (Ogura et al, 1986;Ananth et al, 1987;Bartrup and Newberry, 1994;Elliott et al, 1995;Kagaya et al, 1995;Pauwels et al, 1996).…”

Section: Discussionsupporting

confidence: 95%

In vitro evidence that 5‐hydroxytryptamine increases efflux of glial glutamate via 5‐HT_2A receptor activation

Meller

Harrison

Elliott

et al. 2002

J of Neuroscience Research

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Recent studies have established the presence of 5-hydroxytryptamine (5-HT)(2A) receptors on glial cells in culture and in the brain in situ. Here we used cultured C6 glioma cells to investigate the possibility that 5-HT(2A) receptors on glia regulate glutamate release from the cell. The efflux of endogenous glutamate from cultured C6 glioma cells was increased by addition of 5-HT in a concentration-dependent manner (maximal effect +200%). The efflux of serine and aspartate was not altered. The effect of 5-HT was mimicked by both the nonselective 5-HT receptor agonist quipazine and the selective 5-HT(2) receptor agonist 4-iodo-2,5-dimethoxyamphetamine (DOI; both 0.01-100 microM). The 5-HT(2A) receptor antagonists ketanserin (1 microM) and spiperone (1 microM) inhibited the glutamate response to 5-HT, quipazine, and DOI, whereas the effect of 5-HT was not inhibited by the 5-HT(2B/C) receptor antagonist SB200646 (1 microM). The effect of 5-HT on glutamate was specific in that it was reduced in low-calcium medium but was not prevented by furosemide (5 mM), which prevents cell swelling-induced glutamate release. Finally, the glutamate uptake inhibitor 2,4,trans-pyrollidine dicarboxylic acid (50 microM) did not block the 5-HT-induced efflux of glutamate, making involvement of glutamate transport unlikely. In conclusion, 5-HT stimulates the efflux of glutamate from C6 glioma cells following 5-HT(2A) receptor activation and involves a calcium-dependent mechanism.

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Section: Discussionsupporting

confidence: 95%

In vitro evidence that 5‐hydroxytryptamine increases efflux of glial glutamate via 5‐HT_2A receptor activation

Meller

Harrison

Elliott

et al. 2002

J of Neuroscience Research

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“…These results indicate that 5-HT? receptors are involved in in ducing intracellular Ca2+ mobilization, confirming and extending the conclusions of Ananth et al [ 12] who con cluded that C6 cells contained a 5-HT:-like receptor, based on their results of the partial inhibition of the 5-HT response by mianserin [12].…”

Section: Discussionsupporting

confidence: 75%

“…Rat glioma cells (C6BU-I) have a substantial number of [S-adrenergic receptors that are tightly coupled to ade nylate cyclase and have proved to be a useful model for studying the phenomenon of desensitization and downregulation ofjf-adrenergic receptors [7][8][9][10][11], In these cells, the only indication of the existence of 5-HT receptors is the capacity of the neurotransmitter to cause an enhance ment of phosphoinositide hydrolysis [12] and an increase in intracellular free Ca2+ in a suspension of C6BU-1 cells [13]. ft remained uncertain as to what subclass of 5-HT receptors they might belong and what the consequences of their stimulation might be.…”

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confidence: 99%

Dexamethasone Potentiates Serotonin-2 Receptor-Mediated Intracellular Ca<sup>2+</sup> Mobilization in C6 Glioma Cells

et al. 1993

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Serotonin (5-hydroxytryptamine; 5-HT) caused a transient increase in intracellular Ca²⁺ in C6BU-1 glioma cells in a concentration-dependent manner; half maximally at 73 nM. The 5-HT₂ agonist 1-(4-iodo-2,5-dimethoxyphenyl)-2-aminopropane also increased the levels of intracellular Ca²⁺ whereas the 5-HTιc agonist l-(3-chlorophenyl)piperazine and 5-HT_1a agonist 8-hydroxy-2-(di-n-propylamino)tetralin were completely ineffective. Ketanserin and spiperone blocked the response to 5-HT at a nanomolar concentration, but the 5-HT3 antagonist MDL 72222 had no effect on it. Thus 5-HT₂ receptors are responsible for activating Ca²⁺ mobilization in C6 glioma cells. Treatment of C6 glioma cells with dexamethasone potentiated the ability of 5-HT to cause intracellular Ca²⁺ mobilization in both a dose- and time-dependent manner. The dose-response curve for 5-HTwas shifted 9-fold to the left compared to controls, and the V_max value was also significantly enhanced. This enhanced Ca²⁺ mobilization was completely inhibited by ketanserin dose-dependently. In addition, the treatment with dexamethasone enhanced fluoride-activated Ca²⁺ mobilization, suggesting that the enhanced GTP binding protein function is one of the mechanisms responsible for the enhancement of the 5-HT response induced by dexamethasone treatment. This enhancement of agonist activity was mediated by the type II glucocorticoid receptor (GR) since RU 38486, an inhibitor of the type II GR, antagonized the dexamethasone-induced enhancement.

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“…In the current study, we have examined the effect of both agonist and antagonist exposure on 5-HT 2A receptor function in C6 glioma cells. C6 glioma cells endogenously express the 5-HT 2A receptor, which is coupled to the stimulation of phospholipase C (Ananth et al, 1987;Ding et al, 1993). Furthermore, 5-HT 2A receptors are down-regulated in C6 glioma cells by antagonist treatment (Toth and Shenk, 1994), as has been observed in vivo (Blackshear and Sanders-Bush, 1982;Anji et al, 2000), making these cells an appropriate model system.…”

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confidence: 87%

Mechanisms of Ligand-Induced Desensitization of the 5-Hydroxytryptamine_2AReceptor

Hanley

Hensler

2002

J Pharmacol Exp Ther

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We have examined the cellular processes underlying the desensitization of the 5-hydroxytryptamine (5-HT) 2A receptor induced by agonist or antagonist exposure. Treatment of C6 glioma cells with either 5-HT or the 5-HT 2A receptor antagonist ketanserin resulted in an attenuation in 5-HT 2A receptor function, specifically the accumulation of inositol phosphates stimulated by the partial agonist quipazine. 5-HT-induced desensitization of the 5-HT 2A receptor involved receptor internalization through a clathrin-and dynamin-dependent process because it was prevented by concanavalin A, monodansylcadaverine, and by expression of the dominant negative mutants ␤-arrestin (319 -418) and dynamin K44A. Although short-term (i.e., 10 min) 5-HT and ketanserin exposure resulted in the same degree of desensitization, ketanserin-induced desensitization was not prevented by these agents and did not involve receptor internalization. In contrast, prolonged ketanserin exposure (i.e., 2 h) resulted in 5-HT 2A receptor internalization through a clathrinand dynamin-dependent process, as was observed after agonist treatment. Inhibitors of protein kinase C or calcium-calmodulin kinase II did not attenuate or prevent 5-HT-induced desensitization of the receptor. 5-HT 2A receptor desensitization induced by 5-HT and prolonged ketanserin treatment, but not by short-term ketanserin treatment, was prevented by the expression of the dominant negative mutant of G protein-coupled receptor kinase (GRK)2, GRK2-K220R, and by an anti-GRK2/3 antibody. Our data indicate a dual mechanism of early and late desensitization by the antagonist ketanserin. Short-term ketanserin treatment reduced the specific binding of the agonist radioligand Desensitization of G protein-coupled receptors occurs during agonist exposure, often in a matter of minutes. Mechanisms underlying the desensitization of many G proteincoupled receptors have been elucidated in part by using the ␤-adrenergic receptor as a prototype (Bunemann and Hosey, 1999). In this "classical" multistep process, the agonist-occupied state of the receptor is phosphorylated by a second messenger-dependent kinase (e.g., protein kinase A) and/or a G protein-coupled receptor kinase (GRK). The binding of an adapter protein, arrestin, leads to uncoupling of the receptor from the G protein and receptor sequestration through clathrin-coated vesicles. The internalization of the receptor is dependent on dynamin, a GTPase that is responsible for pinching off the endocytotic vesicle. Internalized receptors may be returned to the cell surface, or degraded in lysosomes.The 5-hydroxytryptamine (5-HT) 2A receptor has been implicated in the mechanism of action of many psychoactive drugs such as hallucinogens, atypical neuroleptics, and antidepressants. The regulation of the 5-HT 2A receptor, however, does not appear to follow the pattern established for many other G protein-coupled receptors. Repeated administration of agonists (Buckholtz et al., 1988;Anji et al., 2000) as well as antagonists (Blackshear and Sande...

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Stimulation of Phosphoinositide Hydrolysis by Serotonin in C6 Glioma Cells

Cited by 58 publications

References 47 publications

In vitro evidence that 5‐hydroxytryptamine increases efflux of glial glutamate via 5‐HT_2A receptor activation

In vitro evidence that 5‐hydroxytryptamine increases efflux of glial glutamate via 5‐HT_2A receptor activation

Dexamethasone Potentiates Serotonin-2 Receptor-Mediated Intracellular Ca<sup>2+</sup> Mobilization in C6 Glioma Cells

Mechanisms of Ligand-Induced Desensitization of the 5-Hydroxytryptamine_2AReceptor

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Stimulation of Phosphoinositide Hydrolysis by Serotonin in C6 Glioma Cells

Cited by 58 publications

References 47 publications

In vitro evidence that 5‐hydroxytryptamine increases efflux of glial glutamate via 5‐HT2A receptor activation

In vitro evidence that 5‐hydroxytryptamine increases efflux of glial glutamate via 5‐HT2A receptor activation

Dexamethasone Potentiates Serotonin-2 Receptor-Mediated Intracellular Ca<sup>2+</sup> Mobilization in C6 Glioma Cells

Mechanisms of Ligand-Induced Desensitization of the 5-Hydroxytryptamine2AReceptor

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In vitro evidence that 5‐hydroxytryptamine increases efflux of glial glutamate via 5‐HT_2A receptor activation

In vitro evidence that 5‐hydroxytryptamine increases efflux of glial glutamate via 5‐HT_2A receptor activation

Mechanisms of Ligand-Induced Desensitization of the 5-Hydroxytryptamine_2AReceptor