Receptor-mediated calcium signals in astroglia: multiple receptors, common stores and all-or-nothing responses.
Cell Calcium
; 17(3): 187-96, 1995 Mar.
Article
em En
| MEDLINE
| ID: mdl-7621532
ABSTRACT
Calcium signals following activation of P2Y purinergic, alpha 1 adrenergic, and muscarinic cholinergic receptors were examined in individual astroglial cells. ATP, phenylephrine and carbachol, each increased intracellular calcium levels ([Ca2+]i) to similar amplitudes in the presence or absence of extracellular Ca2+. The dose-response relationship showed that less than an order of magnitude increase in ligand concentration led to maximal increase in [Ca2+]i from basal levels. Simultaneous application of multiple ligands did not produce additive effects on [Ca2+]i. These data suggested that different ligands released Ca2+ from common stores and that each of the ligands could cause maximal release. Application of a second ligand immediately after the first ligand produced an additional Ca2+ rise, suggesting that the Ca2+ stores were rapidly refilled and that receptor desensitization rather than Ca2+ depletion accounted for the rapid decline of the Ca2+ peak. Caged IP3 produced Ca2+ signals similar to those produced by ligands. For a given cell, both caged IP3 and ligands sometimes produced only one level of partial Ca2+ increases, suggesting the presence of a pool of high IP3-sensitive stores. Together, our results indicate that neuroligands tend to generate an all-or-nothing Ca2+ release from IP3 sensitive stores. The interactions between different receptor systems most likely occur at the level of IP3 accumulation.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Transdução de Sinais
/
Astrócitos
/
Cálcio
/
Receptores de Neurotransmissores
Limite:
Animals
Idioma:
En
Ano de publicação:
1995
Tipo de documento:
Article