A sequential two-step priming scheme reproduces diversity in synaptic strength and short-term plasticity

Area of Science:

• Neuroscience
• Synaptic Plasticity
• Molecular Biology

Background:

• Glutamatergic synapses show variable strength and short-term plasticity (STP).
• Understanding the mechanisms behind this diversity is crucial for neuroscience.
• Existing models do not fully capture the nuances of synaptic vesicle release dynamics.

Purpose of the Study:

• To develop a kinetic model that explains the diversity of STP in glutamatergic synapses.
• To investigate the primary determinants of synaptic strength and STP.
• To refine quantal analysis methods for a better mechanistic understanding of synaptic function.

Main Methods:

• Nonnegative tensor factorization.
• Conventional state modeling.
• Kinetic scheme modeling synaptic vesicle (SV) docking, priming, and fusion.

Main Results:

• A kinetic scheme with two priming steps and fusion accurately reproduces STP diversity.
• Synaptic strength and STP variations are mainly due to the fraction of docked SVs with mature release machinery, not fusion probability.
• Traditional quantal analysis may not solely reflect fusion probability but also priming states.

Conclusions:

• The proposed kinetic model provides a mechanistic explanation for synaptic strength and STP diversity.
• The fraction of maturely primed SVs is a key determinant of synaptic efficacy.
• This framework aids in dissecting presynaptic protein functions in SV release and suggests activity-dependent synaptic efficacy modulation.