Bursting induces persistent all-or-none EPSPs by an NMDA-dependent process in piriform cortex.

Area of Science:

• Neuroscience
• Cellular Electrophysiology
• Neuroplasticity

Background:

• Olfactory cortex neurons exhibit complex responses to stimulation.
• Extracellular ion concentrations (Mg2+, Cl-) critically influence neuronal excitability.
• Long-lasting changes in neuronal properties are fundamental to neural function.

Purpose of the Study:

• To investigate long-lasting neuronal changes in the olfactory cortex following induced bursting activity.
• To characterize the properties of a novel, high-amplitude depolarizing potential.
• To explore the role of NMDA receptors in the generation of this late potential.

Main Methods:

• Induction of bursting activity in olfactory cortex slices by altering extracellular Mg2+ or Cl- concentrations.
• Electrophysiological recordings of pyramidal cell responses to afferent and associational fiber stimulation.
• Application of NMDA receptor antagonists (APV, ketamine) during bursting activity.

Main Results:

• Bursting activity induced a persistent, high-amplitude, all-or-none depolarizing potential in pyramidal cells.
• This late potential, resembling an excitatory postsynaptic potential (EPSP), exhibited a discrete threshold and long duration.
• NMDA receptor antagonists prevented the development of the late potential but did not affect its expression once established.

Conclusions:

• A novel, synchronized neuronal event, likely an EPSP, is generated in the olfactory cortex after bursting activity.
• The development of this late potential depends on NMDA receptor activation during the initial bursting.
• These findings offer insights into the neuronal mechanisms underlying long-term memory and epilepsy.