Enduring medial perforant path short-term synaptic depression at high pressure.

Area of Science:

• Neuroscience
• Physiology
• Biophysics

Background:

• High pressure neurological syndrome (HPNS) affects cognitive function during deep diving.
• Synaptic frequency-dependent depression (FDD) is crucial for neuronal network function.
• The medial perforant path (MPP) synapses exhibit FDD under normal conditions.

Purpose of the Study:

• Investigate the effects of high pressure (HP) and extracellular calcium ([Ca(2+)](o)) on MPP synapse FDD.
• Determine how HP and [Ca(2+)](o)] interact to modulate synaptic transmission.
• Analyze the impact of HP on synaptic resources.

Main Methods:

• Utilized rat cortico-hippocampal slices.
• Employed computer simulations for analysis.
• Measured synaptic responses (fEPSPs) under varying pressure and calcium conditions.

Main Results:

• HP (10.1 MPa) depressed single MPP field EPSPs (fEPSPs) by 50%.
• Elevated [Ca(2+)](o) at HP saturated synaptic responses but maintained FDD similar to atmospheric pressure.
• Mathematical modeling indicated HP reduces synaptic resources, impacting synaptic activity.

Conclusions:

• HP affects MPP synapses by depressing single events and reducing synaptic resources.
• The interaction between HP and [Ca(2+)](o)] suggests a mechanism for preserving synaptic dynamics.
• These findings offer insights into neural adaptations to high-pressure environments.