Taste responses of the facial and glossopharyngeal nerves to amino acids in the rainbow trout

No significant differences were noted between responses of rainbow trout Oncorhynchus mykiss facial and glossopharyngeal nerves to 15 amino acids. Nine of these amino acids tested at 10⁻² M were stimulatory, whereas only two tested at 10⁻³ M were effective gustatory stimuli. For both nerve systems, ≤10⁻³ M L-proline was the most stimulatory amino acid, with an estimated threshold of 10⁻⁷ M; however, L-α-amino-β-guanidino-propionic acid (estimated threshold of 3×10⁻³ M), was the most potent compound at 10⁻² M. These results indicate that the same amino acids activate taste buds innervated by facial and glossopharyngeal nerves, respectively, and suggest that the same amino acids can be important in chemosensory feeding behaviour in the rainbow trout.