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Developmental decrease in synaptic facilitation at the mouse hippocampal mossy fibre synapse.
Fumiko Mori-Kawakami1, Katsunori Kobayashi, Tomoyuki Takahashi
1Department of Neurophysiology, University of Tokyo Graduate School of Medicine, Tokyo 113-0033, Japan.
The Journal of Physiology
|September 10, 2003
Summary
Hippocampal mossy fibre (MF) synaptic facilitation decreases with development. This change is linked to residual calcium dynamics, not release probability, impacting hippocampal circuit stability.
Area of Science:
- Neuroscience
- Synaptic Plasticity
- Developmental Biology
Background:
- Hippocampal mossy fibre (MF) synapses exhibit activity-dependent facilitation, crucial for dynamic range in information processing.
- This facilitation is known to change significantly during postnatal development.
Purpose of the Study:
- To investigate the developmental mechanisms underlying the decrease in MF-CA3 synaptic facilitation from 3 to 9 weeks in mice.
- To determine if changes in release probability, presynaptic receptors, protein kinases, or calcium dynamics explain this developmental shift.
Main Methods:
- Paired-pulse stimulation and extracellular Ca2+/Mg2+ manipulation to assess facilitation and release probability.
- Measurement of unitary excitatory postsynaptic current (EPSC) amplitude and variance.
- Monitoring presynaptic Ca2+ transients using mag-fura-5.
- Pharmacological inhibition of specific receptors and kinases.
- Intracellular BAPTA buffering to probe the role of residual calcium.
Main Results:
- Paired-pulse and frequency-dependent facilitation significantly decreased between 3 and 9 weeks, while EPSC amplitude and variance remained constant.
- Altering extracellular Ca2+/Mg2+ changed facilitation but with large shifts in EPSC amplitude, inconsistent with developmental changes.
- Presynaptic Ca2+ transients showed similar facilitation magnitudes at both ages.
- Pharmacological agents targeting receptors and kinases did not account for the developmental change.
- BAPTA loading reduced facilitation more in younger mice, diminishing the age-dependent difference.
Conclusions:
- The developmental decrease in MF synaptic facilitation is primarily attributed to altered residual calcium handling, either reduced levels or changes in calcium-binding sites.
- This developmental decline in facilitation impacts the dynamic range of MF transmission, potentially contributing to hippocampal circuit stabilization.