The smelling of Hedione results in sex-differentiated human brain activity

A large family of vomeronasal receptors recognizes pheromone cues in many animals including most amphibia, reptiles, rhodents, and other mammals. Humans possess five vomeronasal-type 1 receptor genes (VN1R1-VN1R5), which code for proteins that are functional in recombinant expression systems. We used two different recombinant expression systems and identified Hedione as a ligand for the putative human pheromone receptor VN1R1 expressed in the human olfactory mucosa. Following the ligand identification, we employed functional magnetic resonance imaging (fMRI) in healthy volunteers to characterize the in vivo action of the VN1R1 ligand Hedione. In comparison to a common floral odor (phenylethyl alcohol), Hedione exhibited significantly enhanced activation in limbic areas (amygdala, hippocampus) and elicited a sex-differentiated response in a hypothalamic region that is associated with hormonal release. Utilizing a novel combination of methods, our results indicate that the putative human pheromone receptor VN1R1 is involved in extra-olfactory neuronal activations induced by the odorous substance Hedione. The activation of VN1R1 might play a role in gender-specific modulation of hormonal secretion in humans.