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Ca2+ Sensitivity of Synaptic Vesicle Dopamine, ?-Aminobutyric Acid, and Glutama...
Gonçalves, Paula P.; Meireles, Sandra M.; Neves, Paulo; Vale, M. Graça P.The effect of Ca2+ on the uptake of neurotransmitters by synaptic vesicles was investigated in a synaptic vesicle enriched fraction isolated from sheep brain cortex. We observed that dopamine uptake, which is driven at expenses of the proton concentration gradient generated across the membrane by the H+-ATPase activity, is strongly inhibited (70%) by 500 µM Ca2+. Conversely, glutamate uptake, which essentially ...
Distinction between Ca2+ pump and Ca2+/H+ antiport activities in synaptic vesic...
Gonçalves, Paula P.; Meireles, Sandra M.; Neves, Paulo; Vale, M. Graça P.Synaptic vesicles, isolated from a sheep brain cortex, accumulate Ca2+ in a manner that depends on the pH and pCa values. In the presence of 100 [mu]M CaCl2, most of the Ca2+ taken up by the vesicles was vanadate-inhibited (86%) at pH 7.4, whereas at pH 8.5, part of the Ca2+ accumulated (36%) was [Delta]pH-dependent (bafilomycin and CCCP inhibited) and part was insensitive to those drugs (31%). We also observed...
Methods for analysis of Ca2+/H+ antiport activity in synaptic vesicles isolated...
Gonçalves, Paula P.; Meireles, Sandra M.; Neves, Paulo; Vale, M. Graça P.The involvement of Ca2+-storage organelles in the modulation of synaptic transmission is well-established [M.K. Bennett, Ca2+ and the regulation of neurotransmitter secretion, Curr. Opin. Neurobiol. 7 (1997) 316-322 [1]; M.J. Berridge, Neuronal calcium signaling, Neuron 21 (1998) 13-26 [2]; Ph. Fossier, L. Tauc, G. Baux, Calcium transients and neurotransmitter release at an identified synapse, Trends Neurosci. ...
Synaptic vesicle Ca2+/H+ antiport: dependence on the proton electrochemical gra...
Gonçalves, Paula P.; Meireles, Sandra M.; Neves, Paulo; Vale, M. Graça P.Synaptic vesicles isolated from sheep brain cortex accumulate Ca2+ by a mechanism of secondary active transport associated to the H+-pump activity. The process can be visualized either by measuring Ca2+-induced H+ release or [Delta]pH-dependent Ca2+ accumulation. We observed that the amount of Ca2+ taken up by the vesicles increases with the magnitude of the [Delta]pH across the membrane, particularly at Ca2+ c...
Ionic selectivity of the Ca2+/H+ antiport in synaptic vesicles of sheep brain c...
Gonçalves, Paula P.; Meireles, Sandra M.; Neves, Paulo; Vale, M. Graça P.As we previously reported, synaptic vesicles isolated from sheep brain cortex contain a Ca2+/H+ antiport that permits Ca2+ accumulation inside the vesicles (~5 nmol/mg protein) at expenses of the pH gradient generated by the H+-pumping ATPase. We observed that the system associates Ca2+ influx to H+ release and operates with low affinity for Ca2+. In the present work, we found that Ca2+/H+ antiport mediates exc...
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