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  • Title: Inhibition of high voltage-activated calcium currents by L-glutamate receptor-mediated calcium influx.
    Author: Zeilhofer HU, Müller TH, Swandulla D.
    Journal: Neuron; 1993 May; 10(5):879-87. PubMed ID: 8098610.
    Abstract:
    The modulation of high voltage-activated (HVA) Ca2+ currents by L-glutamate and its agonists was investigated in cultured rat hypothalamic neurons. L-Glutamate and agonists selective for NMDA or non-NMDA receptors reversibly inhibited HVA Ca2+ currents. The putative presynaptic glutamate receptor agonist L-2-amino-4-phosphonobutyric acid and the selective metabotropic agonist trans-ACPD were ineffective. Inhibition was dependent on the presence of extracellular Ca2+ and blocked by internal perfusion of the cells with BAPTA. The calmodulin antagonists trifluoperazine and calmidazolium completely prevented the inhibition. Increases in the intracellular Ca2+ concentration due to Ca2+ influx through non-NMDA receptor channels were visualized using fura-2. These results indicate that not only NMDA but also non-NMDA receptor channels in these neurons are permeable for Ca2+ and that Ca2+ influx through these channels activates a calmodulin-dependent mechanism, which leads to HVA Ca2+ current inhibition.
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