Insulin modulates network activity in olfactory bulb slices: impact on odour processing.

Area of Science:

• Neuroscience
• Olfactory System
• Hormonal Regulation

Background:

• Odour perception is linked to nutritional status in humans and animals.
• Insulin, a key hormone regulating appetite, is implicated in connecting olfactory abilities with nutritional state.
• The olfactory bulb (OB) is a primary target for insulin's central actions.

Purpose of the Study:

• To investigate how insulin affects the olfactory bulb (OB).
• To evaluate insulin's action on mitral cells (MCs), the main output neurons of the OB.
• To understand the impact of insulin on olfactory processing related to nutritional status.

Main Methods:

• Electrophysiological recordings from acute rat OB slices.
• Assessment of insulin's effects on mitral cell (MC) excitability and synaptic activity.
• Mathematical modeling to analyze population activity and functional consequences.

Main Results:

• Insulin increases MC excitability, likely via potassium channel inhibition.
• Insulin modulates GABAergic and glutamatergic synaptic inputs to MCs, primarily reducing them.
• Insulin alters olfactory nerve (ON)-evoked responses in MCs, decreasing high firing rates and increasing low rates, thus reducing response variability.
• Mathematical modeling indicates that reduced MC variability impacts odour detection and discrimination, with effects varying by odour quality.

Conclusions:

• Insulin acts at multiple levels within the OB network.
• Insulin's differential modulation of MCs based on firing rate links olfactory function to nutritional status.
• This hormonal control allows olfactory perception to adapt to the body's feeding signals and metabolic state.