, Volume 147, Issue 2, pp 217-229

Taste and tactile recordings from the ramus recurrens facialis innervating flank taste buds in the catfish

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Summary

  1. The ramus recurrens facialis (VII) innervating the flank of the channel catfish,Ictalurus punctatus, responded to both amino acid (Fig. 2–10; Table 1) and mechanical (Fig. 11) stimulation of the flank skin.

  2. The integrated phasic gustatory responses generally increased exponentially with logarithmic increase in stimulus concentration over a wide concentration range with a tendency for saturation at concentrations ≧10−4.5 M (Fig. 6).

  3. l-alanine andl-arginine HCl were the most stimulatory compounds tested, with thresholds averaging 10−8.6±0.4m (M±SE) (Fig. 4; Table 1).

  4. Cross-adaptation experiments suggest that alanine and arginine bind to relatively independent receptor sites on the taste cells (Fig. 10; Table 1); further, single-unit studies indicate the recurrent nerve is composed of at least two types of amino acid sensitive taste fibers, alanine-best and arginine-best fibers (Fig. 8). In general, unit responses were consistent with the multiunit data (Table 1).

  5. Taste fibers of the recurrent nerve are relatively insensitive to sodium chloride and sucrose; generally, responses were obtained to quinine hydrochloride and hydrochloric acid, but only at relatively high stimulus concentrations (≧10−4 M, Fig. 7).

  6. Taste responses of the recurrent nerve are similar to the results obtained from maxillary barbel taste recordings in the same species (Caprio 1975, 1978), suggesting an analogous chemical response profile of facially innervated taste buds irrespective of their anatomical location in the catfish.

  7. Intra-cranial neural recordings from the recurrent nerve indicate that the tactile responsiveness observed in the present experiments was not attributable to spinal innervation of the flank. The size and contour of the mechanoreceptive flank region innervated by teased bundles of the recurrent nerve varied greatly; some single units responded to both chemical and mechanical stimuli (Fig. 11).