Taste responses to amino acids from facial nerve branches innervating oral and extra-oral taste buds in the channel catfish, Ictalurus punctatus.

Electrophysiological recordings were obtained from two branches of the facial nerve innervating oral and extra-oral taste receptive fields, respectively, in the channel catfish, Ictalurus punctatus. The results indicate that taste buds innervated by the ramus ophthalmicus superficialis (ros), innervating taste buds on the nasal barbel, and the ramus palatinus (rp), innervating taste buds on the anterior palate, have similar chemical specificities for amino acids. Among the amino acids tested, the most stimulatory compounds for both the ros and rp were L-alanine and L-arginine, having estimated electrophysiological thresholds of approximately 10(-9) M. Dose-response functions for amino acid stimuli recorded from both the ros and rp were power functions extending over 5 log units of stimulus concentrations. The general similarity in the nature of the taste input from spatially distinct gustatory areas supports a chemotactic role of the facial taste system in the channel catfish.