Spike-timing-dependent plasticity in hippocampal CA3 neurons.

Area of Science:

• Neuroscience
• Synaptic Plasticity
• Hippocampal Function

Background:

• Mossy fibre (MF) input to CA3 pyramidal neurons is crucial for hippocampal function.
• MF plasticity is often considered distinct, being NMDAR-independent and presynaptic.
• This study investigates MF plasticity under specific timing conditions.

Purpose of the Study:

• To investigate spike-timing-dependent plasticity at the mossy fibre (MF) input to CA3 neurons.
• To determine the role of postsynaptic activity and NMDA receptor (NMDAR) activation in MF plasticity.
• To explore bidirectional changes in synaptic efficacy.

Main Methods:

• Using electrophysiological recordings in 3-week-old rats.
• Employing specific stimulation protocols to pair excitatory postsynaptic potentials (EPSPs) with postsynaptic action potentials (APs).
• Utilizing NMDAR blockers to assess their role in plasticity induction.

Main Results:

• Long-term potentiation (LTP) was induced when EPSPs preceded APs by 10 ms.
• Long-term depression (LTD) was induced when APs were delayed by 30 ms relative to EPSPs.
• Both LTP and LTD were dependent on postsynaptic NMDAR activation, indicating postsynaptic expression.

Conclusions:

• Spike-timing-dependent plasticity at the MF-CA3 synapse is bidirectional.
• This plasticity is critically dependent on postsynaptic NMDA receptor activation.
• The findings challenge the notion of MF plasticity being universally NMDAR-independent.