[Electrophysiological evaluation of mediator secretion and pool at an individual point of neuromuscular synapse release in the frog].
The time-course of one-quantum end plate potentials during repetitive stimulation of the motor nerve (5-10 imp/sec) was studied under iontophoretic application of Ca2+ to the nerve ending with the aid of high-resistance exocellular microelectrodes. It was found that long-term stimulation was first accompanied by rapid and then by a slower decrease of transmitter release. After 2 to 3 minutes of stimulation the level of secretion reached a plateau. Blockade of acetylcholine synthesis by hemicholinium-3 did not affect the time-course of transmitter secretion drop but led to the disappearance of the plateau state. Electrophysiological study of transmitter exchange in an individual point of release provided the following values: the available transmitter pool 32-47 quanta, the mobilization pool 120-320 quanta, the rate of transmitter synthesis 0.3-1.0 quanta/s.
D000200:Action Potentials; D000818:Animals; D004558:Electric Stimulation; D004594:Electrophysiology; D066298:In Vitro Techniques; D008564:Membrane Potentials; D009045:Motor Endplate / Q000502:physiology; D009469:Neuromuscular Junction / Q000378:metabolism*; D018377:Neurotransmitter Agents / Q000378:metabolism*; D011898:Ranidae; D012584:Sciatic Nerve / Q000502:physiology; D013569:Synapses / Q000378:metabolism*
D018377:Neurotransmitter Agents
Elektrofiziologicheskaia otsenka sekretsii i zapasa mediatora v otdel'noĭ tochke osvobozhdeniia nervno-myshechnogo sinapsa liagushki.