Effect of feeding and fasting on plasma tryptophan and tryptophan to large neutral amino acid ratio,and on brain serotonin turnover in rainbow trout,Oncorhynchus mykiss |
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| Authors: | W L Johnston N T Glanville |
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| Institution: | (1) Department of Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada, NIG 2W1;(2) Present address: Department of Neurology, McGill University, Montreal General Hospital Research Institute, 1650 Cedar Ave., Montreal, Quebec, Canada, H3G 1A4;(3) Present address: Human Ecology Department, Mount Saint Vincent University, Halifax, Nova Scotia, Canada, B3M 2J6 |
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| Abstract: | Two time-course experiments were conducted to determine the effect of feeding and fasting on the plasma ratio of tryptophan (trp) to the large neutral amino acids (LNAA), (trp/LNAA ratio) and brain serotonin (5-HT) turnover in rainbow trout,Oncorhynchus mykiss. Trout were fasted overnight or for 3 days and were then either fed or continued to be fasted for up to a further 3 days. Changes in plasma trp, plasma trp/LNAA ratio, brain trp, brain 5-HT, brain 5-hydroxyindoleacetic acid (5-HIAA) and brain 5-HIAA/5-HT ratio were determined over time. Feeding decreased the plasma trp/LNAA ratio, brain trp and the brain 5-HIAA/5-HT ratio. In addition, in fish sampled over 3 days, there appeared to be a rhythm in plasma trp and the brain 5-HIAA/5-HT ratio which was independent of feeding. These results indicate that in rainbow trout, feeding is a sufficient physiological event to decrease brain 5-HT turnover. Furthermore, feeding-independent changes in the brain 5-HIAA/5-HT ratio, which were evident in fasted fish sampled over 3 days, also suggest an additional, non-feeding-related modulator(s) of brain 5-HT turnover in rainbow trout. |
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| Keywords: | 5-HT 5-hydroxytryptamine serotonin tryptophan trp/LNAA rainbow trout Oncorhynchus mykiss food intake |
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