Short-term plasticity in glomerular inhibitory circuits shapes olfactory bulb output

Area of Science:

• Neuroscience
• Olfactory System
• Synaptic Plasticity

Background:

• Short-term plasticity is crucial for neural processing and memory.
• Olfactory information is transmitted via glomerular microcircuits involving excitatory and inhibitory neurons.
• Olfactory input is driven by episodic sniffing, suggesting frequency-dependent modulation.

Purpose of the Study:

• To investigate frequency-dependent short-term plasticity in olfactory glomerular inhibitory circuits.
• To determine how this plasticity influences mitral/tufted cell (M/TC) outputs.
• To understand the role of short axon cells (SACs) and periglomerular cells (PGCs) in olfactory processing.

Main Methods:

• Used channelrhodopsin-2 (ChR2) viral delivery in GAD2-cre and TH-cre mice.
• Selectively activated SACs and PGCs while recording from other cell populations or M/TCs.
• Assessed synaptic inhibition and short-term plasticity at various activation frequencies (1-20 Hz).

Main Results:

• Confirmed reciprocal inhibitory connections between SACs and PGCs.
• SAC inhibition of PGCs showed facilitation at 5-10 Hz; PGC inhibition of SACs was frequency-independent.
• Both SAC and PGC inhibition of M/TCs exhibited plasticity in the 5-20 Hz range, corresponding to sniffing frequencies.
• SAC synapses markedly suppressed M/TC spiking.

Conclusions:

• Olfactory glomerular inhibitory networks are sensitive to input frequencies, particularly investigative sniffing rates.
• Short-term plasticity dynamically shapes glomerular output signals to downstream targets.
• Episodic sniffing input differentially regulates intra- and interglomerular inhibitory circuits.