Postsynaptic conversion of silent synapses during LTP affects synaptic gain and transmission dynamics.

Area of Science:

• Neuroscience
• Synaptic Plasticity
• Cellular Electrophysiology

Background:

• Synaptic transmission involves both signal gain and temporal dynamics.
• Activity-dependent synaptic plasticity, crucial for brain information storage, is well-documented at excitatory synapses.
• Mechanisms underlying changes in synaptic transmission dynamics remain an active area of research.

Purpose of the Study:

• To investigate the mechanisms driving changes in transmission dynamics at excitatory synapses.
• To elucidate the role of silent synapses in synaptic plasticity and signal transmission.
• To understand how paired-pulse ratios (PPRs) of AMPA and NMDA receptor EPSCs change during long-term potentiation (LTP).

Main Methods:

• Electrophysiological recordings of AMPA receptor (AMPAR) and NMDA receptor (NMDAR) EPSCs in dentate gyrus granule cells.
• Paired-pulse stimulation protocols to assess synaptic dynamics.
• Manipulation of presynaptic function.
• Analysis of synaptic transmission changes during LTP induction.

Main Results:

• Paired-pulse ratios (PPRs) of AMPAR and NMDAR EPSCs were often dissimilar, with this difference diminishing during LTP.
• LTP induction primarily altered AMPAR EPSC PPRs, not NMDAR EPSC PPRs.
• Presynaptic manipulations induced parallel changes in both AMPAR and NMDAR EPSCs.
• LTP was associated with a decrease in the proportion of silent synapses lacking functional AMPARs.
• Changes in PPR during LTP reflect the initial disparity between PPRs of silent and functional synapses.

Conclusions:

• The functional conversion of silent synapses contributes to altered synaptic dynamics during LTP.
• This conversion allows postsynaptic neurons to sample from additional release sites, impacting signal gain and dynamics.
• Understanding these mechanisms provides insight into information processing and storage in the brain.