Mixture and concentration effects on odorant receptor response patterns in vivo

Area of Science:

• Neuroscience
• Olfactory receptor function
• Chemical senses

Background:

• Natural odors are complex mixtures of volatile chemicals (odorants).
• Olfactory sensory neurons express hundreds of odorant receptors (ORs) and trace amine-associated receptors (TAARs) to encode odors.
• Odor perception is complicated by dose-response relationships and odorant interactions at receptors, leading to phenomena like mixture suppression.

Purpose of the Study:

• To investigate in vivo odorant receptor response patterns in freely behaving mice.
• To examine how odorant concentration affects receptor response patterns.
• To explore in vivo interactions between different odorants at the receptor level.

Main Methods:

• In vivo electrophysiological recordings in freely behaving mice.
• Stimulation with single odorants and odorant mixtures at varying concentrations.
• Analysis of olfactory sensory neuron responses to identify receptor activation patterns and interactions.

Main Results:

• Confirmed a characteristic receptor response pattern with a few strongly responding receptors and many weakly responding ones.
• Demonstrated that odorant receptor response patterns broaden with increasing odorant concentration.
• Observed suppression of responses to indole (fecal odorant) by α-ionone (floral odorant), indicating in vivo odorant interactions.

Conclusions:

• Odor encoding relies on specific, albeit complex, receptor response patterns.
• Concentration-dependent broadening of receptor responses may contribute to concentration-invariant odor perception.
• In vivo odorant interactions at receptors are common and significantly impact olfactory processing.