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  • Title: [Ion currents of a nerve ending in the sartorius muscle of the frog].
    Author: Zefirov AL, Khalilov IA.
    Journal: Neirofiziologiia; 1985; 17(6):770-9. PubMed ID: 2418373.
    Abstract:
    Nerve terminal responses evoked by motor nerve, stimulation were recorded from frog sartorius nonmyelinated endings by external electrodes. At proximal parts of nerve terminal a triphasic waveform (+ - +) was observed. Ionophoretic application of tetrodotoxin, tetraethylammonium and 4-aminopyridine indicated that the negative phase reflected inward sodium current while the third positive phase--outward potassium current. Using solutions with tubocurarine from which calcium was omitted and an electrode filled with CaCl2 a late slow negative response component was recorded. This component depended on Ca2+ concentration in the electrode, increased with addition of tetraethylammonium and 4-aminopyridine and was abolished by Co2+. A similar component was recorded by microelectrodes filled with solutions containing Sr2+ and Ba2+ ions. It is concluded that the slow component of the response reflects the current across potential-dependent calcium channels in the presynaptic membrane. The time courses of calcium current and transmitter release in the synapse are compared.
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