ABSTRACT
This chapter presents the results of studies characterizing possible transduction steps in the amino acid taste system of the channel catfish, Ictalurus punctatus. This animal has been shown to possess at least two major classes of discrete receptors for stimulus amino acids. Given the wide concentration range across which the amino acids are stimulatory and the complexity of many of the binding isotherms of these stimuli for their putative receptors, it is very likely that multiple receptors (or receptor sites) exist for each major stimulus class. Both cyclase catalytic activity and PIP2-PDE enzyme activity were stimulated by low levels of the potent taste stimulus L-alanine with the time course of second-messenger accumulation consistent with a primary role in transduction for either or both of these second-messenger systems. However, before the roles of cyclic AMP and the inositol phospholipids in taste transduction can be understood, additional research needs to be completed.
