Inositol 1,4,5-trisphosphate induced mobilization of Ca2+ from rat brain synaptosomes |
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Authors: | C. R. Gandhi D. H. Ross |
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Affiliation: | (1) Division of Molecular Pharmacology, Department of Pharmacology, The University of Texas Health Science Center, 7703 Floyd Curl Drive, 78284-7764 San Antonio, Texas |
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Abstract: | Inositol 1,4,5-trisphosphate (IP3) was found to release Ca2+ from presynaptic nerve endings (synaptosomes) made permeable with saponin. ATP-dependent Ca2+ uptake was carried out until equilibrium was reached. Addition of IP3 produced a rapid release of Ca2+, which was complete within 60 sec, followed by Ca2+ reaccumulation to the original level in 5–7 min. Cholinergic receptor stimulation with muscarine also produced a similar Ca2+ release from synaptic endoplasmic reticulum. Ca2+ release by IP3 was not detectable in the absence of the mitochondrial inhibitors oligomycin or sodium azide. Reaccumulation of Ca2+ was prevented by the presence of vanadate, a potent inhibitor of Ca2+/Mg2+ ATPase. Half maximal and near complete release of Ca2+ took place at 0.4 M and 3 M IP3 concentrations, respectively. These studies demonstrate for the first time IP3 mobilization of Ca2+ from endoplasmic reticulum within synaptic plasma membranes. |
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Keywords: | Calcium synaptosomes inositol 1,4,5-trisphosphate |
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