Periglomerular cell action on mitral cells in olfactory bulb shown by current source density analysis.

Area of Science:

• Neuroscience
• Olfactory System Research
• Cellular Electrophysiology

Background:

• The interaction between periglomerular (PG) cells and mitral cells is crucial for olfactory signal processing.
• Understanding the precise mechanism of PG cell action on mitral cells is key to deciphering olfactory bulb circuitry.

Purpose of the Study:

• To investigate the sign of action of periglomerular (PG) cells on the apical dendrites of mitral cells.
• To elucidate the role of PG cells in olfactory bulb network dynamics using electrophysiological recordings.

Main Methods:

• Current source density (CSD) profiles were constructed from evoked potentials.
• Electrode arrays recorded potentials from anesthetized rabbit olfactory bulbs during primary olfactory nerve (PON) and lateral olfactory tract (LOT) stimulation.
• One-dimensional CSD analysis was performed at specific time points (N1, P1, N2) of the average evoked potential (AEP).

Main Results:

• A secondary source-sink pair, indicative of excitation, was observed in the glomerular layer (GL) and outer plexiform layer (EPL) during PON stimulation, but not LOT stimulation.
• This excitation was localized to the GL and GL/EPL border, suggesting prolonged mitral cell activation.
• CSD analysis revealed that PG cell activity likely contributes to this long-lasting excitation of mitral cells.

Conclusions:

• The findings support the direct excitatory action of periglomerular (PG) cells onto mitral cells.
• PG cell activity, potentially combined with prolonged monosynaptic PON excitation, underlies the observed long-lasting excitation of mitral cells.
• This study clarifies a fundamental interaction within the olfactory bulb's neural circuitry.