Functional Olfactory Receptor Research Articles

The olfactoryL-serine receptor in coho salmon: biochemical specificity and behavioral response

1. The specificity of the olfactory receptor site forl-serine in coho salmon,Oncorhynchus kisutch, was evaluated by using biochemical receptor and behavioral assays of olfaction. 2. A competitive binding experiment showed that the ability of amino acids to compete for thel-serine binding site depended on molecular size and charge.l-threonine,l-serine, andl-alanine were best able to compete withl-serine suggesting that the threonine-serine-alanine (TSA) odor binding site exists in coho salmon. 3. The behavioral response to singly-presented amino acids was evaluated by using a two-choice Y-trough. Threonine, serine, alanine, and histidine were behaviorally avoided at 10−7M. All other amino acids tested were neither aversive nor attractive. 4. A cross-adaptation experiment indicated that the detection and behavioral avoidance of serine was inhibited by the adapting amino acids serine, alanine, or glycine but not by threonine, aspartic acid, or histidine. 5. A classical conditioning experiment showed that single fish were unable to discriminate between serine and alanine but were able to discriminate serine or alanine from a qualitatively different odor such as histidine. 6. These results, taken together, indicate thatl-serine andl-alanine were functionally identical odors to coho salmon. We propose that a functional olfactory receptor site for serine and alanine (site SA) exists in coho salmon.