Reciprocal connectivity between mitral cells and external plexiform layer interneurons in the mouse olfactory bulb

Area of Science:

• Neuroscience
• Olfactory System Research
• Cellular Neurobiology

Background:

• Proper brain function depends on the balance of excitation and inhibition.
• Inhibitory circuits in the olfactory bulb, like those involving granule cells, refine odor processing by inhibiting mitral cells.

Purpose of the Study:

• To investigate potential inhibitory connections onto mitral cells by other local interneurons.
• To characterize a novel circuitry involving Corticotropin-Releasing Hormone (CRH)-expressing interneurons in the olfactory bulb's external plexiform layer (EPL).

Main Methods:

• Utilized cell type-specific genetic manipulations.
• Employed advanced imaging techniques.
• Performed optogenetic stimulation and electrophysiological recordings.

Main Results:

• Identified a novel, strongly connected, and reciprocal circuit between CRH-expressing EPL interneurons and mitral cells.
• Demonstrated that CRH-expressing EPL interneurons significantly inhibit mitral cell firing.
• Revealed that these interneurons are reciprocally excited by mitral cell glutamatergic input.

Conclusions:

• Functionally identified a new subpopulation of olfactory bulb interneurons with reciprocal connectivity to mitral cells.
• Uncovered a previously unknown component of olfactory bulb circuitry.
• This finding suggests a new player that may influence olfactory processing and lateral interactions.