Fraction of action potentials that trigger release from most presynaptic nerve terminals

Range 10 - 20 % of action potentials
Organism Unspecified
Reference Sudhof TC. The synaptic vesicle cycle. Annu Rev Neurosci. 2004 27: 509-47. p.509 bottom paragraphPubMed ID15217342
Primary Source Goda Y, Sudhof TC. 1997. Calcium regulation of neurotransmitter release: reliably unreliable. Curr. Opin. Cell Biol. 9: 513–18PubMed ID9261057
Comments "Synaptic transmission is initiated when an action potential triggers neurotransmitter release from a presynaptic nerve terminal (Katz 1969). An action potential induces the opening of Ca2+ channels, and the resulting Ca2+ transient stimulates synaptic vesicle exocytosis (Figure 1). After exocytosis, synaptic vesicles undergo endocytosis, recycle, and refill with neurotransmitters for a new round of exocytosis. Nerve terminals are secretory machines dedicated to repeated rounds of release. Most neurons form >500 presynaptic nerve terminals [BNID 111276] that are often widely separated from the neuronal cell bodies. Action potentials, initiated in the neuronal cell body, travel to all of the cell body’s nerve terminals to be transformed into synaptic secretory signals. Nerve terminals do not convert reliably every action potential into a secretory signal but are “reliably unreliable” (primary source). In most terminals, only 10%–20% of action potentials trigger release. The relationship between action potentials and release in a nerve terminal is regulated by intracellular messengers and extracellular modulators and is dramatically altered by repeated use of a synapse. Thus in addition to secretory machines, nerve terminals are computational units where the relation of input (action potential) to output (neurotransmitter release) continuously changes in response to extra- and intracellular signals."
Entered by Uri M
ID 111277