Chemoreception Mechanisms in Aquatic Animals

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During collaborative interactions in 1995 & 1996 among the investigators, Drs.N.Suzuki, K.Kurihara, J.Caprio, T.Valentincic and T.Marui, a better understanding of the chemoreception mechanisms in aquatic animals, specifically in fishes was realized. in addition, research directions for future studies were outlined. Specific accomplishments of their collaborative interactions include : (1) Collaborative experiments improved the yield and viability of siolated olfactory and gustatory receptor cells from teleosts, rainbow trout, bullhead catfish and carp. The chemical specificity of single olfactory receptor neurons in fishes resulted in continuing studies to confirm that individual olfactory receptor neurons respond to multiple amino acids that bind to independent receptors, and that single receptor neurons of fish often respond to amino acids wih a suppression of their spontaneous activity. ; (2) Discussions concerning the homing mechanisms of euryharine fishes resulted in a conclusion … More that olfactory responses to amino acids are not influenced by changes in ionic environments surrounding olfactory organs, and that the salmon May discriminate the home river by the olfactory clue based on the content of different amino acids in the river water. ; (3) The pervasiveness of neurons within central "gustatory" nuclei that are sensitive to both taste and tactile stimulation resulted in a conclusion that peripheral facial fibers in the catfish can be responsive to only taste, to only tactile or to both taste and tactile stimulation. Thus, the bimodality of central neurons could occur by either the convergence of taste only and tactile only fibers or by bimodal fibers themselves. The suppressive effects of quinine on teleost taste systems resulted in a hypothesis based primarily on the anti-malarial research on quinine, i.e.a blocking effect on calcium channels. ; (4) Collaborative experiments on olfactory conditionings of bullhead catfish resulted in a conclusion that the catfish conditioned to a single amino acid can discriminate it from other single amino acids, and that binary mixtures of amino acids are discriminated by physiologically more stimulatory component within the mixture. ; (5) A candidate of cDNA for a G-protein that may involve in the taste transduction was cloned with a PCR technique and its expression in the apical part of taste cells of carp barbels was confirmed by using a DIG probe technique. Less