Local dendritic activity sets release probability at hippocampal synapses

Area of Science:

• Neuroscience
• Synaptic Plasticity
• Cellular Signaling

Background:

• Synaptic efficacy is determined by neurotransmitter release probability (p(r)).
• Mechanisms controlling basal p(r) at individual synapses remain largely unknown.
• p(r) varies significantly across synapses, impacting neural circuit function.

Purpose of the Study:

• To investigate the factors determining basal release probability at individual synapses.
• To explore the relationship between local dendritic activity and synaptic release probability.
• To understand the homeostatic regulation of synaptic transmission.

Main Methods:

• Measurement of p(r) at single presynaptic terminals in connected hippocampal neuron pairs.
• Analysis of p(r) in relation to neighboring synapses on the same dendritic branch.
• Manipulation of dendritic depolarization and activity levels.

Main Results:

• Neighboring synapses exhibit similar release probabilities.
• Release probability (p(r)) is negatively correlated with the number of synapses per dendritic branch.
• Increased dendritic depolarization induces a homeostatic decrease in p(r).
• Synchronized dendritic activity reduces p(r) variability.

Conclusions:

• Local dendritic activity is a primary determinant of basal synaptic release probability.
• Activity-dependent feedback regulation of p(r) may maintain synapses within their functional range.
• This homeostatic mechanism contributes to stable neural circuit operation.