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Developmental changes in short-term synaptic depression in the neonatal mouse spinal cord
1Laboratory of Neural Control, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892-4455, USA.
Journal of Neurophysiology
|December 6, 2002
Summary
Synaptic depression in mouse spinal cords lessens with age due to reduced neurotransmitter release. Recovery rates remained consistent, suggesting developmental changes primarily impact release rather than resource renewal.
Area of Science:
- Neuroscience
- Developmental Biology
- Synaptic Plasticity
Background:
- Short-term synaptic depression is crucial for regulating neuronal activity.
- Understanding its developmental trajectory is key to deciphering neural circuit maturation.
Purpose of the Study:
- To investigate age-dependent changes in short-term synaptic depression in mouse spinal motoneurons.
- To elucidate the underlying mechanisms, particularly presynaptic release dynamics.
Main Methods:
- Recorded excitatory postsynaptic potentials (EPSPs) in mouse lumbar motoneurons from postnatal day 2 to 12.
- Utilized paired-pulse, steady-state, irregular stimulation, and recovery paradigms.
- Applied quantitative models of presynaptic release and resource dynamics.
Main Results:
- Synaptic depression decreased with postnatal age, particularly paired-pulse and during irregular stimulation.
- Synaptic recovery rates after conditioning trains showed minimal age-dependent changes.
- Presynaptic transmitter release was identified as the primary factor influencing these changes.
Conclusions:
- Reduced presynaptic release fraction significantly contributes to the decline in synaptic depression during early postnatal development.
- Developmental changes in release fraction, not resource renewal, shape synaptic depression.
- A quantitative model with two depleted compartments and two release-enhancing mechanisms accurately predicted the data.