Antagonistic interactions between odorants alter human odor perception.

Area of Science:

• Olfactory neuroscience
• Molecular biology
• Sensory perception

Background:

• The olfactory system utilizes hundreds of odorant receptors (ORs), the largest G-protein-coupled receptor (GPCR) family, to detect diverse odorants.
• Antagonism, the blocking of receptor activation, is a known mechanism in GPCRs, and recent evidence suggests it influences olfactory neuron activity in odor mixtures.
• However, the precise impact of odorant antagonism on the perception of complex odor mixtures remains incompletely understood.

Purpose of the Study:

• To identify human ORs activated by methanethiol and hydrogen sulfide, potent malodorous volatile sulfur compounds.
• To screen for odorant antagonists that block the activation of these identified ORs.
• To investigate the effect of identified antagonists on human perception of malodors.

Main Methods:

• Large-scale heterologous expression of human ORs.
• Screening of odorants for their ability to block OR activation in cell-based assays.
• Human sensory evaluation to assess the impact of antagonists on odor perception.

Main Results:

• Identification of specific human ORs activated by methanethiol and hydrogen sulfide.
• Discovery of β-ionone as an antagonist that blocks OR activation by methanethiol.
• Human sensory tests confirmed that β-ionone significantly reduced the perceived intensity and unpleasantness of methanethiol odor.
• Suppression of methanethiol odor was not observed when presented to a different nostril than β-ionone, suggesting direct interaction.

Conclusions:

• Odor sensation is modulated by antagonistic interactions occurring at the odorant receptor (OR) level.
• This finding supports the hypothesis that blocking OR activation by specific odorants can alter the perception of complex smells.
• The study provides a molecular basis for understanding how odor mixtures are perceived and how certain compounds can modify the sensory experience of others.