D-AP5 blocks the increase of intracellular free Ca2+ induced by glutamate in isolated cochlear IHCs / 中华医学杂志(英文版)
Chinese Medical Journal
; (24): 89-93, 2002.
Article
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| ID: wpr-308131
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ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effect of D-AP5 (D-2-amino-5-phosphonopentanoate, a specific NMDA-antagonist) on the increase of intracellular free Ca2+ concentration ([Ca2+]i) induced by glutamate in isolated cochlear inner hair cells (IHCs), and to detect the autoreceptors of the IHC membrane.</p><p><b>METHODS</b>When a laser scanning confocal microscope (LSCM) was used, the exogenous glutamate (Glu)-induced changes in [Ca2+]i of isolated IHCs and OHCs of guinea pig cochlea were observed with fluo-3, a fluorescent probe for [Ca2+]i. After D-AP5 or CNQX (6--cyano--7--nitroguinoxaline--2, 3--dione, a specific AMPA- antagonist) was administered, the exogenous glutamate (Glu)-induced changes in [Ca2+]i of isolated IHCs were recorded.</p><p><b>RESULTS</b>In the presence of a low concentration Glu (3.85 mumol/L), there was an increase of [Ca2+]i in IHCs, whereas there was no change in OHCs. When 50 mumol/L of D-AP5 was administrated in advance, Glu did not induce a corresponding increase in [Ca2+]i in IHCs, and 50 mumol/L of CNQX did not completely block the increase of [Ca2+]i in IHCs.</p><p><b>CONCLUSIONS</b>These results suggest that the autoreceptors existing in the IHC membrane are mainly of NMDA type, while there are relatively few AMPA receptors. Exogenous Glu is capable of increasing [Ca2+]i in IHCs by acting on the NMDA autoreceptor of IHCs in a positive feedback manner.</p>
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WPRIM
Asunto principal:
Farmacología
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Técnicas In Vitro
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2-Amino-5-fosfonovalerato
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Calcio
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Receptores de N-Metil-D-Aspartato
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6-Ciano 7-nitroquinoxalina 2,3-diona
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Ácido Glutámico
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Antagonistas de Aminoácidos Excitadores
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Cobayas
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Células Ciliadas Auditivas Internas
Límite:
Animals
Idioma:
En
Revista:
Chinese Medical Journal
Año:
2002
Tipo del documento:
Article