Concanavalin A application to the olfactory epithelium reveals different sensory neuron populations for the odour pair D- and L-carvone.
Carvone enantiomers (D and L optical isomers) have been shown to be discriminable by humans even though the odor qualities are quite similar. Our experiment is based on a finding (J. Steroid Biochem. Molec. Biol. 1991;39(4B):621) that Concanavalin A (ConA) applied to a frog olfactory epithelium preparation blocks cAMP transduction induced by D- but not by L-carvone. We used standard operant conditioning methods to train animals to discriminate low odor concentrations of D-carvone from clean air, to discriminate L-carvone from clean air; or to discriminate between clean air and the odors of D-carvone, L-carvone, ethyl acetate and methacrylic acid. After perfusion of the nasal cavity with ConA, rats did not respond to D-carvone above or near chance level, while the L-carvone response was not affected at the same or higher ConA doses. However, for rats trained on both enantiomers and the two other unrelated odorants, the D-carvone response remained unaffected by ConA. These results suggest to us that: (1) ConA blocks at least one chiral receptor selective for D-carvone; (2) D-carvone odor quality is modified by ConA so that it is no longer recognized by rats trained on D-carvone only, while rats trained to generalize odors still respond to D-carvone.
Kirner
Alexandra
A
Institute of Zoology, Animal Physiology, University of Tübingen, Auf der Morgenstelle 28, D-72076 Tubingen, Germany.
Deutsch
Swetlana
S
Weiler
Elke
E
Polak
Ernest H
EH
Apfelbach
Raimund
R
D000818:Animals; D002628:Chemoreceptor Cells / Q000187:drug effects*; D003208:Concanavalin A / Q000494:pharmacology*; D000081005:Cyclohexane Monoterpenes; D004193:Discrimination Learning / Q000187:drug effects*; D008297:Male; D039821:Monoterpenes; D009831:Olfactory Mucosa / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D012684:Sensory Thresholds / Q000187:drug effects; D012903:Smell / Q000187:drug effects*; D013237:Stereoisomerism; D013729:Terpenes
D000081005:Cyclohexane Monoterpenes; D039821:Monoterpenes; D013729:Terpenes; D003208:Concanavalin A; C006923:carvone