Effect of an oral tryptophan/carbohydrate load on tryptophan, large neutral amino acid, and serotonin and 5-hydroxyindoleacetic acid levels in monkey brain.
TL;DR: While tryptophan administration can stimulate serotonin production in primate brain, the effect may be restricted to certain brain regions, and it is suggested that the transport of the large neutral amino acids into brain occurs via a competitive mechanism similar to that for other mammals.
Abstract: Plasma and brain levels of tryptophan and other large neutral amino acids, and brain levels of serotonin and 5-hydroxyindoleacetic acid (5 HIAA) were measured in groups of adult cynomolgus monkeys 1 hr after they ingested one of four doses of a tryptophan-carbohydrate mixture. The doses had been administered once daily for 13 weeks. Dose-related increments occurred in plasma tryptophan, the plasma ratio of tryptophan to the sum of other large neutral amino acids, and in brain tryptophan levels. In contrast, the plasma ratios and brain levels of the other neutral amino acids each declined. Serotonin and 5 HIAA levels increased significantly, and in, a dose-related manner in the brainstem and striatum, but not in cortex or hypothalamus. The results suggest that while tryptophan administration can stimulate serotonin production in primate brain, the effect may be restricted to certain brain regions. They also suggest that the transport of the large neutral amino acids into brain occurs via a competitive mechanism similar to that for other mammals.
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TL;DR: There is now convincing evidence that exercise-induced increases in the plasma free tryptophan (f-TRP)/branched-chain amino acids (BCCA) ratio are associated with increased brain 5-HT and the onset of fatigue during prolonged exercise.
Abstract: The mechanisms of central fatigue are largely unexplored, but the central fatigue hypothesis suggests that increased brain serotonin (5-HT) can cause a deterioration in sport and exercise performance. There is now convincing evidence that exercise-induced increases in the plasma free tryptophan (f-TRP)/branched-chain amino acids (BCCA) ratio are associated with increased brain 5-HT and the onset of fatigue during prolonged exercise. Furthermore, when drugs are administered to alter brain 5-HT, they have the predicted effects on exercise performance. The influence of nutritional manipulations of f-TRP/BCCA on performance is less well established. The effects of BCCA supplementation on exercise performance are mixed, and the published studies often suffer from methodological flaws. Alternatively, dramatic reductions in f-TRP/BCCA and enhanced performance accompany carbohydrate feedings during prolonged exercise. However, it is difficult to distinguish between the effects of carbohydrate feedings on mechanis...
99 citations
TL;DR: The development of animal models that may capture the complexity of 5-HT-ergic interactions promises to afford a powerful tool to elucidate the pathophysiology of impulsive aggression and suicidability, and identify new effective therapies for these conditions.
89 citations
Cites background from "Effect of an oral tryptophan/carboh..."
...Considering the brain concentrations of tryptophan, TPH is not expected to be saturated with substrate, and the formation of 5-HT in brain is predicted to rise as the brain concentration of tryptophan increases (Leathwood and Fernstrom, 1990)....
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TL;DR: It would appear that the combination of this 5-HT manipulation and cocaine administration altered the reinforcing efficacy of the drug and induced a long-term decrement in breaking point under a progressive ratio schedule.
Abstract: l -Tryptophan (100 mg/kg, IP), the serotonin [5-hydroxytryptamine (5-HT)] amino acid precursor, significantly reduced the mean breaking point maintained under a self-administration progressive ratio schedule of IV cocaine reinforcement (0.6 mg/injection). This effect was produced over the 5 days of self-administration following treatment. Responding maintained under the same progressive ratio schedule for food reinforcement was not affected by l -tryptophan (100 mg/kg, IP). Rats administered l -tryptophan (100 mg/kg, IP) and denied access to cocaine on the day of treatment resumed normal self-administration patterns under a progressive ration schedule on following test days. This indicates that l -tryptophan treatment alone did not induce long-term effects on cocaine self-adminisration. Thus, it would appear that the combination of this 5-HT manipulation and cocaine administration altered the reinforcing efficacy of the drug and induced a long-term decrement in breaking point under a progressive ration schedule. This may have been due to an associative aversion to cocaine self-administration behaviour learned on the day of treatment and carried over to the subsequent 5 days of self-administration access.
77 citations
TL;DR: Changing meal compositions influence platelet-poor plasma serotonin (5-HT) and norepinephrine (NE) levels and the resulting changes in PPP 5-HT levels parallel those reported for brain neurotransmitters, and results seem to indicate that PPP 4- HT levels may be a model for brain synthesis and release of 5- HT.
Abstract: Reports concerning changes in plasma neurotransmitter values that result from dietary manipulations have not been published so far. The influence of various meal composition on platelet-poor plasma (PPP) serotonin (5-HT) and norepinephrine (NE) levels was investigated. Healthy volunteers were subjected to three test meals: a carbohydrate-rich meal (86% carbohydrates), a protein-rich meal (70% protein), and a fat-rich meal (92% fat). After a carbohydrate-rich meal, PPP 5-HT values increased significantly (4.47-fold, P
54 citations
TL;DR: It was determined that day-to-day variability in free plasma TP and the percentage of protein binding produced most of the variability in the calculated serotonin synthesis rates, and it seems that the [11C;[alpha;MTP model for the computation ofotonin synthesis rates is very dependent on plasma free TP concentration and that it may not accurately determine actual serotonin synthesis rate.
40 citations
References
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01 Jan 1983
4,887 citations
"Effect of an oral tryptophan/carboh..." refers methods in this paper
...All statistical analyses were carried out using the BMDP statistical package (Dixon, 1983)....
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TL;DR: The main determinant of brain tryPTophan and serotonin concentrations does not appear to be plasma tryptophan alone, but the ratio of this amino acid to other plasma neutral amino acids that compete with it for uptake into the brain.
Abstract: When plasma tryptophan is elevated by the injection of tryptophan or insulin, or by the consumption of carbohydrates, brain tryptophan and serotonin also rise; however, when even larger elevations of plasma tryptophan are produced by the ingestion of protein-containing diets, brain tryptophan and serotonin do not change. The main determinant of brain tryptophan and serotonin concentrations does not appear to be plasma tryptophan alone, but the ratio of this amino acid to other plasma neutral amino acids (that is, tyrosine, phenylalanine, leucine, isoleucine, and valine) that compete with it for uptake into the brain.
1,090 citations
TL;DR: Brain serotonin cocentrations at 1 p.m. were significantly elevated 1 hour after rats received a dose of L-tryptophan and plasma and brain tryptophan levels were elevated 10 to 60 minutes after the injection, but they never exceeded the concentrationis that occur nocturnally in untreated aninmals as result of their normal 24-hour rhythms.
Abstract: Brain serotonin cocentrations at 1 p.m. were significantly elevated 1 hour after rats received a dose of L-tryptophan (12.5 milligrams per kilogram. intraperitoneally) smaller than one-twentieth of the normal daily dietary intake. Plasma and brain tryptophan levels were elevated 10 to 60 minutes after the injection, but they never exceeded the concentrationis that occur nocturnally in untreated aninmals as result of their normal 24-hour rhythms. These data suggest that physiological changes in plasma tryptophan concentration influenice brain serotonin levels.
980 citations
"Effect of an oral tryptophan/carboh..." refers background in this paper
...Data supporting this notion derive mainly from studies in animals, including rats (Ashcroft et al., 1965; Fernstrom and Wurtman, 1971), cats (Ternaux et al., 1976), and dogs (Moir and Eccleston, 1968)....
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...Data supporting this notion derive mainly from studies in animals, including rats (Ashcroft et al., 1965; Fernstrom and Wurtman, 1971), cats (Ternaux et al....
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TL;DR: The specificity of the method is such that, of the compounds tested, only tryptamine produces appreciable fluorescence: one tenth of the molar fluorescence of tryptophan.
791 citations
"Effect of an oral tryptophan/carboh..." refers methods in this paper
...Plasma and cerebral cortical TRP levels were measured in aliquots of plasma and cortical supernatants using an adaptation of the fluorimetric method of Denckla and Dewey (Bloxam and Warren, 1974; Denckla and Dewey, 1967; Lehmann, 1971)....
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TL;DR: The diet‐induced changes in the brain level of each of the amino acids also correlate surprisingly well with the calculated rate of brain influx for each amino acid.
Abstract: — The brain levels of each of the aromatic and branched-chain amino acids change 2 h after fasting rats begin to consume either a carbohydrate-fat diet or a similar diet containing 18% or 40% protein. Carbohydrate-fat ingestion elevates the concentrations of each of the aromatic amino acids in brain, while substantially depressing those of the branched-chain amino acids. The inclusion of protein in this diet suppresses the increases in brain aromatic amino acids and attenuates the decreases in the branched-chain amino acids. The changes in the brain level of each neutral amino acid following the ingestion of any of these diets correlate extremely well with the effects of the diet on the serum neutral amino acid pattern, specifically on the serum concentration ratio of each neutral amino acid to the sum of the other neutral amino acids. The diet-induced changes in the brain level of each of the amino acids also correlate surprisingly well with the calculated rate of brain influx for each amino acid.
407 citations