Persistent synapse loss induced by repetitive LTD in developing rat hippocampal neurons

Area of Science:

• Neuroscience
• Developmental Biology
• Synaptic Plasticity

Background:

• Synaptic pruning is crucial for normal neural development, eliminating excess synapses.
• The precise mechanisms governing synaptic pruning remain incompletely understood.
• Synaptic activity strength is hypothesized to guide synapse elimination.

Purpose of the Study:

• To investigate the role of long-term depression (LTD) in synaptic pruning during neuronal development.
• To determine if repetitive LTD induction affects synapse number in developing hippocampal neurons.
• To elucidate the molecular mechanisms underlying LTD-induced synaptic pruning.

Main Methods:

• Cultured rat hippocampal neurons at 14 days in vitro were used.
• Repetitive induction of LTD was achieved using a group I metabotropic glutamate receptor (mGluR) agonist (DHPG).
• Synapse number was quantified following triple LTD induction, with or without mGluR antagonists (MCPG).

Main Results:

• Multiple LTD inductions, but not single, led to a persistent reduction in dendritic synapse number.
• This reduction was observed in proximal dendrites and lasted for at least two weeks.
• The effect was blocked by the simultaneous application of a group I/II mGluR antagonist (MCPG).

Conclusions:

• Repetitive LTD induction acts as a trigger for synaptic pruning in developing hippocampal neurons.
• This finding highlights the contribution of activity-dependent processes to synapse elimination.
• Metabotropic glutamate receptors play a key role in mediating LTD-induced synaptic pruning.