Evidence of distinct amino acid and bile salt receptors in the olfactory system of the zebrafish, Danio rerio.

The molecular receptors for amino acid and bile salt odorants of adult zebrafish, Danio rerio, were partially characterized using electro-olfactogram recording methods. Each of the 14 odorants tested interact with partially independent odorant receptor(s). Based on shared patterns of adaptation, cluster analysis identified two very dissimilar groups of odorants. The first group comprised the 8 amino acids with subgroups of basic, acidic and neutral amino acids. The second group comprised the 6 bile salts with subgroups of non-conjugated, taurine- and glycine-conjugated bile salts. Comparison of the general patterns of partial adaptation of amino acid and bile salt odorants suggests fundamental differences in their odorant receptors. Presumably, the differences in the extent of partial adaptation are due to differences in the transduction cascades activated or the distribution of odorant receptors on individual olfactory receptor neurons.