Paired-pulse facilitation of transmitter release at different levels of extracellular calcium concentration.
High-frequency synaptic activity can cause facilitation of transmitter release due to accumulation of "residual Ca(2+)" at the nerve terminal. However, the mechanism of this phenomenon is still under debate. Here we show that, using extracellular recording from frog cutaneous pectoris muscle, paired-pulse facilitation (PPF) at the frog neuro-muscular junction decays in two or three-exponential manner depending upon the extracellular Ca(2+) concentration ([Ca(2+)](e)). First, second and "early" PPF components are analyzed and described in this study. Considering the dependence of PPF on [Ca(2+)](e), existence of several specific high-affinity intra-terminal Ca(2+)-binding sites that underlie the facilitation of transmitter release at the frog neuro-muscular junction is proposed.
Mukhamedyarov
Marat A
MA
Department of Physiology, Kazan State Medical University, ul. Butlerova 49, 420012 Kazan, Russia.
Zefirov
Andrey L
AL
Palotás
András
A
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004558:Electric Stimulation; D004594:Electrophysiology; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000378:metabolism; D009469:Neuromuscular Junction / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000378:metabolism*; D011895:Rana ridibunda; D009435:Synaptic Transmission / Q000502:physiology*
D018377:Neurotransmitter Agents; D002118:Calcium