Presynaptic residual calcium and synaptic facilitation at hippocampal synapses of mice with altered expression of SNAP-25.
Brain Res
; 1431: 1-12, 2012 Jan 11.
Article
in En
| MEDLINE
| ID: mdl-22119397
ABSTRACT
Paired pulse facilitation (PPF) is a form of short-term synaptic plasticity that results from an interaction of residual presynaptic Ca(2+) ([Ca(2+)](res)), number of release-competent vesicles, and the sensitivity of the vesicle release mechanisms to Ca(2+). While PPF is predominant at hippocampal Schaffer collateral-CA1 (SC-CA1) synapses, facilitation is greater in adult mice (designated Tkneo) that over express an isoform of the plasma membrane-targeted SNARE protein, SNAP-25a, which is normally predominantly expressed in juvenile animals. SNAP-25 is essential for action potential-dependent neuroexocytosis, yet the significance of the shift between the alternatively spliced variants SNAP-25a and SNAP-25b is not fully understood. This alteration of a key component of the protein machinery required for neurotransmitter release in Tkneo mice, therefore, provides a useful tool to further investigate presynaptic mechanisms that influence short-term plasticity. To explore this link between SNAP-25 and PPF, we simultaneously measured postsynaptic potentials and presynaptic [Ca(2+)](res) during paired-pulses in adult Tkneo, heterozygote null (HET), and wild type (WT) mice. We demonstrate that enhanced PPF is maintained at mature hippocampal synapses of Tkneo mice that predominantly express SNAP-25a, and that [Ca(2+)](res) kinetics are altered at synapses of Tkneo and HET mice, both of which exhibit reduced levels of total SNAP-25 expression. To evaluate the role of SNAP-25 in short-term plasticity and [Ca(2+)](res) regulation, we applied a vesicular release probability model for neurotransmission. Our results suggest that the isoform expression and total level of SNAP-25 affect both [Ca(2+)](res) dynamics and the ability of releasable vesicles to enter into a facilitated state.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Synapses
/
Calcium
/
Presynaptic Terminals
/
Synaptosomal-Associated Protein 25
/
Hippocampus
Limits:
Animals
Language:
En
Journal:
Brain Res
Year:
2012
Document type:
Article
Country of publication:
HOLANDA
/
HOLLAND
/
NETHERLANDS
/
NL
/
PAISES BAJOS
/
THE NETHERLANDS