Direct cortical inputs erase long-term potentiation at Schaffer collateral synapses

Area of Science:

• Neuroscience
• Synaptic Plasticity
• Hippocampal Function

Background:

• Long-term potentiation (LTP) at hippocampal Schaffer collateral (SC) synapses is crucial for memory.
• The role of direct entorhinal cortex input via the perforant path (PP) to CA1 is less understood.

Purpose of the Study:

• To investigate the effect of perforant path stimulation on Schaffer collateral synaptic transmission in the hippocampus.
• To elucidate the mechanisms underlying synaptic plasticity modulation by cortical inputs.

Main Methods:

• Low-frequency stimulation (LFS) of PP inputs to CA1.
• Electrophysiological recordings to assess basal SC transmission and LTP.
• Investigating the involvement of NMDA receptors, metabotropic glutamate receptors, calcium channels, and adenosine receptors.

Main Results:

• LFS of PP inputs did not affect basal SC transmission.
• LFS of PP inputs effectively depotentiated established SC LTP.
• This depotentiation was reversible by high-frequency stimulation of SC inputs.
• Depotentiation involved adenosine acting at A(1) receptors, independent of NMDA, group I mGluRs, or L-type Ca2+ channels.

Conclusions:

• Hippocampal synaptic plasticity can be modulated by cortical inputs.
• Adenosine A(1) receptor-mediated depotentiation of SC synapses provides a mechanism for resetting synaptic strength.
• This process may facilitate information processing and memory consolidation in the hippocampus.