The invention relates to the field of olfactory receptors, conception-influencing medicaments, and biosensors. Disclosed are receptors having a section of the human hOR17-4 gene and receptor proteins that are derived therefrom. Also disclosed are receptors for detecting phenylacetaldehyde, 3-phenylpropanal, 3- phenylbutyraldehyde, 4-phenylbutyraldehyde, canthoxal, cyclamal, floralazone, bourgeonal, lilial, and (4-tert-butylphenoxy)acetaldehyde (agonists). The invention further relates to receptors for said substances, which can be inhibited by applying antagonists, especially n-undecanal. The invention finally relates to advantageous uses of said receptors, agonists, and antagonists.