Ben Aviner, Gideon Gradwohl, Homer J. Moore and Yoram Grossman Modulation of presynaptic Ca2+ currents in frog motor nerve terminals by high pressure European Journal of Neuroscience 38
Pressure effects on terminal Ca2+ currents were studied in frog Rana pipiens peripheral motor nerve. The terminal currents, evoked by nerve or direct stimulation, were recorded under the nerve perineurial sheath. The combined use of Na+ and K+ channel blockers, [Ca2+]o changes, voltage dependent Ca2+ channel (VDCC) blockers treatments, and high pressure (HP) perturbations revealed two components of presynaptic Ca2+ currents: an early fast phase (ICaF) and a late slow and long lasting phase (ICaS). HP reduced the amplitude and decreased the maximum (saturation level) of the Ca2+ currents, the ICaF being more sensitive to pressure. HP also moderately diminished the Na+ action current, which contributed to the depression of VDCC currents. Computer based modeling was used to verify the interpretation of the currents and investigate HP influence on the presynaptic currents. The direct HP reduction of the VDCCs currents and the indirect effect due to action potential decrease are probably the major cause of pressure depression of synaptic release.
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