title: Measurement of intrasynaptosomal free calcium by using the fluorescent indicator quin-2.
abstract: The recently synthesized calcium indicator quin -2 was incorporated into synaptosomes from guinea-pig cerebral cortex following uptake and internal hydrolysis of quin -2 tetra-acetoxymethyl ester. Incubation in physiological media containing 1 mM- or 2 mM-CaCl2 led to equilibrium cytosolic ionized calcium concentrations of 85 +/- 10 nM and 205 +/- 5 nM respectively (mean +/- S.E.M. from eight and eighteen preparations respectively). Cytosolic Ca2+ was elevated following increases in external Ca2+ concentration, plasma membrane depolarization, mitochondrial inhibition, calcium ionophore addition or replacement of external sodium by lithium. Preliminary experiments were performed to assess changes in cytosolic Ca2+ accompanying the release of the neurotransmitter acetylcholine.
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000634:Aminoquinolines; D000818:Animals; D002118:Calcium / Q000032:analysis* / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D005456:Fluorescent Dyes; D006168:Guinea Pigs; D008094:Lithium / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D009435:Synaptic Transmission; D013574:Synaptosomes / Q000032:analysis* / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D000634:Aminoquinolines; D005456:Fluorescent Dyes; D008094:Lithium; D000109:Acetylcholine; C035739:Quin2; D011188:Potassium; D002118:Calcium