caa a22 4500 46576312X CHVBK 20180323111904.0 cr unu---uuuuu 170327e19900301xx s 000 0 eng 10.1007/BF02896921 doi (NATIONALLICENCE)springer-10.1007/BF02896921 4-Aminopyridine stimulates B-50 (GAP-43) phosphorylation in rat synaptosomes [Elektronische Daten] [F. Heemskerk, L. Schrama, P. De Graan, W. Gispen] Recently, we have shown that stimulation of [3H]-noradrenaline release from hippocampal slices by 4-aminopyridine (4-AP) is accompanied by an enhancement of the phosphorylation of B-50, a major presynaptic substrate of protein kinase C (PKC). PKC has been implicated in the regulation of transmitter release. In this study, we investigated the effects of 4-AP on B-50 phosphorylation in synaptosomes from rat brain and compared the effects of 4-AP with those of depolarization with K+, in order to gain more insight into the mechanism of action of 4-AP. B-50 phosphorylation was stimulated by incubation with 4-AP for 2 minutes at concentrations ranging from 10 μM to 5 mM. 4-AP (100 μM) stimulated B-50 phosphorylation already within 15 seconds; longer incubations revealed a sustained increase in the presence of 4-AP. B-50 phosphorylation was also stimulated by depolarization with 30 mM K+ for 15 seconds. The effects of both 4-AP or K+ depolarization on B-50 phosphorylation were abolished at low extracellular Ca2+ concentrations. The increase in B-50 phosphorylation induced by 4-AP seemed to be dependent on the state of depolarization, since the effect of 4-AP was largest under nondepolarizing conditions. Comparing the effects of 4-AP and K+ depolarization on B-50 phosphorylation suggests that a different mechanism of action is involved. These results indicate that the stimulation of B-50 phosphorylation by 4-AP in hippocampal slices can be attributed to a direct action of 4-AP on presynaptic terminals. In addition, our results support the hypothesis that B-50 phosphorylation by PKC is involved in Ca2+-dependent transmitter release evoked by 4-AP. Birkhäuser, 1990 Heemskerk F. Division of Molecular Neurobiology, Institute for Molecular Biology and Medical Biotechnology, Rudolf Magnus Institute, University of Utrecht, Padualaan 8, 3584 CH, Utrecht, The Netherlands aut Schrama L. Division of Molecular Neurobiology, Institute for Molecular Biology and Medical Biotechnology, Rudolf Magnus Institute, University of Utrecht, Padualaan 8, 3584 CH, Utrecht, The Netherlands aut De Graan P. Division of Molecular Neurobiology, Institute for Molecular Biology and Medical Biotechnology, Rudolf Magnus Institute, University of Utrecht, Padualaan 8, 3584 CH, Utrecht, The Netherlands aut Gispen W. Division of Molecular Neurobiology, Institute for Molecular Biology and Medical Biotechnology, Rudolf Magnus Institute, University of Utrecht, Padualaan 8, 3584 CH, Utrecht, The Netherlands aut Journal of Molecular Neuroscience Humana Press 2/1(1990-03-01), 11-17 0895-8696 2:1<11 1990 2 12031 https://doi.org/10.1007/BF02896921 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF02896921 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Heemskerk F. Division of Molecular Neurobiology, Institute for Molecular Biology and Medical Biotechnology, Rudolf Magnus Institute, University of Utrecht, Padualaan 8, 3584 CH, Utrecht, The Netherlands aut NATIONALLICENCE 700 1- Schrama L. Division of Molecular Neurobiology, Institute for Molecular Biology and Medical Biotechnology, Rudolf Magnus Institute, University of Utrecht, Padualaan 8, 3584 CH, Utrecht, The Netherlands aut NATIONALLICENCE 700 1- De Graan P. Division of Molecular Neurobiology, Institute for Molecular Biology and Medical Biotechnology, Rudolf Magnus Institute, University of Utrecht, Padualaan 8, 3584 CH, Utrecht, The Netherlands aut NATIONALLICENCE 700 1- Gispen W. Division of Molecular Neurobiology, Institute for Molecular Biology and Medical Biotechnology, Rudolf Magnus Institute, University of Utrecht, Padualaan 8, 3584 CH, Utrecht, The Netherlands aut NATIONALLICENCE 773 0- Journal of Molecular Neuroscience Humana Press 2/1(1990-03-01), 11-17 0895-8696 2:1<11 1990 2 12031 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer