Research
5-HTP
69 peer-reviewed studies curated from PubMed and Semantic Scholar.
Studies
Sorted by quality and recency
Efficacy of a postbiotic and its components in promoting colonic transit and alleviating chronic constipation in humans and mice.
A randomized, double-blind, placebo-controlled crossover trial with 110 adults and a loperamide-induced mouse model evaluated the efficacy of the postbiotic Probio-Eco in alleviating constipation. The study found significant improvements in constipation symptoms and identified modulations in gut microbiota and metabolomic pathways correlating with symptom relief.
[Clinical evaluation of the efficacy of innovative spread of a given fatty acid composition enriched by adaptogens].
Single-center, single-blind randomized trial evaluating a vegetable-fat spread enriched with 5-hydroxytryptophan, L-theanine, and gamma-aminobutyric acid on memory, well-being, and emotional status in healthy volunteers. The enriched spread improved memory and well-being parameters compared to control.
Tryptophan-enriched diet or 5-hydroxytryptophan supplementation given in a randomized controlled trial impacts social cognition on a neural and behavioral level.
Double-blind placebo-controlled fMRI study with 77 healthy adults investigating the influence of a 4-week tryptophan-enriched diet and acute 5-hydroxytryptophan intake on social-cognitive tasks. 5-HTP led to stricter moral evaluations, and tryptophan improved recognition of positive emotions in older participants, suggesting benefits for social-cognitive processes.
PK/PD modeling of 5-hydroxytryptophan (5-HTP) challenge test with cortisol measurement in serum and saliva.
The study developed a PK/PD model for a 5-HTP challenge test, incorporating a circadian rhythm component of cortisol. Data from three studies in healthy volunteers were used to model the PK of 5-HTP and its effect on cortisol, with a focus on predicting serum cortisol from saliva cortisol.
Effectiveness and safety of treatments for degenerative ataxias: a systematic review.
Systematic review of treatments for degenerative ataxias, including pharmacological, rehabilitative, and psychological therapies. Evidence suggests 5-hydroxytryptophan improves neurological symptoms in certain ataxias, and idebenone is effective for cardiomyopathy in Friedreich ataxia. Limited evidence for other therapies and no significant side effects reported.
Are tryptophan and 5-hydroxytryptophan effective treatments for depression? A meta-analysis.
Meta-analysis reviewing the effectiveness of 5-hydroxytryptophan (5-HT) and L-tryptophan in treating unipolar depression. Two studies with 64 patients met quality criteria, suggesting these substances are better than placebo at alleviating depression, but the small study size and potential publication bias limit the reliability of these findings.
Tryptophan and 5-hydroxytryptophan for depression.
Systematic review evaluating the efficacy of 5-HTP and tryptophan compared to placebo for treating unipolar depression and dysthymia. Only two trials with 64 patients met inclusion criteria, suggesting these substances may be better than placebo at alleviating depression, but evidence quality is insufficient to be conclusive.
Tryptophan and 5-hydroxytryptophan for depression.
Systematic review evaluating the efficacy of 5-HTP and tryptophan compared to placebo for treating depression. Only two trials with 64 patients met inclusion criteria, suggesting these substances may be better than placebo at alleviating depression, but evidence quality is insufficient for conclusive results.
The Impact of 5-Hydroxytryptophan Supplementation on Cognitive Function and Mood in Singapore Older Adults: A Randomized Controlled Trial.
A 12-week randomized controlled trial in Singaporean older adults assessed the effects of 5-HTP supplementation on cognitive function and mood. The 5-HTP group showed significant improvements in cognitive performance and reduced symptoms of depression, with increased serum serotonin levels. No effects were observed on anxiety or other biomarkers.
The impact of 5-hydroxytryptophan supplementation on sleep quality and gut microbiota composition in older adults: A randomized controlled trial.
This randomized controlled trial assessed the impact of 5-HTP supplementation on sleep quality and gut microbiota composition in 30 older adults over 12 weeks. 5-HTP supplementation improved certain sleep quality components and increased microbiota diversity and SCFA-producing bacteria in poor sleepers.
The Effects of 5-HTP on Body Composition: An 8-Week Preliminary RCT.
An 8-week RCT investigating the effects of 100mg daily 5-HTP supplementation on body composition in exercise-trained men and women. The study found a significant decrease in fat mass in the 5-HTP group compared to the placebo group, with no significant changes in lean body mass, total body water, or % body fat.
Preliminary finding of a randomized, double-blind, placebo-controlled, crossover study to evaluate the safety and efficacy of 5-hydroxytryptophan on REM sleep behavior disorder in Parkinson's disease.
RCT of 18 Parkinson's disease patients with REM sleep behavior disorder comparing 5-HTP to placebo over 4 weeks. 5-HTP increased total percentage of stage REM sleep and improved motor experiences of daily living, with marginal improvements in arousal index and wake after sleep onset.
Efficacy and safety of 5-hydroxytryptophan on depression and apathy in Parkinson's disease: a preliminary finding.
A single-center, randomized, double-blind placebo-controlled cross-over trial with 25 participants assessed the effects of 5-HTP on depressive and apathy symptoms in Parkinson's disease. The study found significant improvement in depressive symptoms with 5-HTP compared to placebo, but no effect on apathy symptoms.
Efficacy and safety of 5-Hydroxytryptophan on levodopa-induced motor complications in Parkinson's disease: A preliminary finding.
A single-center, randomized, double-blind placebo-controlled cross-over study with 12 PD patients, 11 of whom completed the protocol, assessed the effects of 5-HTP on levodopa-induced motor complications. The study found significant improvement in LIDs during 50 mg 5-HTP treatment as measured by UDysRS and UPDRS-IV scores.
Effects of oral 5-hydroxytryptophan on a standardized planning task: insight into possible dopamine/serotonin interactions in the forebrain.
RCT with 68 undergraduates testing the effects of 5-HTP on the Tower of London task, a measure of planning and executive control. 5-HTP significantly lengthened the time needed to complete the task, suggesting disruption of dopaminergic function in the forebrain.
L-5-Hydroxytryptophan in the prophylaxis of chronic tension-type headache: a double-blind, randomized, placebo-controlled study. For the Portuguese Head Society.
A double-blind, randomized, placebo-controlled trial with 78 patients with chronic tension-type headaches treated with 5-HTP or placebo for 8 weeks. No significant change in headache days or intensity was observed with 5-HTP, but there was a significant decrease in analgesic consumption and a favorable subjective opinion during the follow-up period.
Endocrine and metabolic changes in transition dairy cows are affected by prepartum infusions of a serotonin precursor.
RCT on 20 Holstein dairy cows to study the effects of prepartum administration of 5-hydroxy-l-tryptophan (5-HTP) on endocrine systems related to calcium homeostasis. The study found that 5-HTP affects calcium homeostasis independent of PTH, with increased pyridinoline concentrations postpartum in the 5-HTP group. No significant effects were observed on other metabolic pathways or IgG concentrations.
Visceral hypersensitivity in irritable bowel syndrome: evidence for involvement of serotonin metabolism--a preliminary study.
Randomized double-blind placebo-controlled study with 15 IBS patients and 15 healthy volunteers assessing the effect of 5-HTP on systemic 5-HT metabolites and visceral perception. 5-HTP induced rectal allodynia in healthy controls and rectal hyperalgesia in hypersensitive IBS patients, with significant changes in 5-HT metabolites observed, particularly in IBS patients.
Serotonergic reinforcement of intestinal barrier function is impaired in irritable bowel syndrome.
Randomised double-blind placebo-controlled study assessing the effects of 5-HTP on mucosal 5-HT availability and intestinal integrity in 15 IBS patients and 15 healthy volunteers. 5-HTP increased mucosal 5-HIAA levels and reinforced intestinal barrier in healthy controls, but not in IBS patients, indicating a dysfunction in serotonin-mediated barrier reinforcement in IBS.
Relationship between the absorption of 5-hydroxytryptophan from an integrated diet, by means of Griffonia simplicifolia extract, and the effect on satiety in overweight females after oral spray administration.
A randomized, double-blind, placebo-controlled trial in 20 overweight females evaluated the effect of Griffonia simplicifolia extract containing 5-hydroxytryptophan on satiety and body composition. The supplemented group showed a significant increase in 24-h urinary 5-HIAA levels and a decrease in appetite and BMI compared to placebo.
An open-label trial of L-5-hydroxytryptophan in subjects with romantic stress.
Open-label trial of L-5-hydroxytryptophan (5-HTP) in 15 young subjects with romantic stress. Significant improvements in romantic stress scores were observed from weeks 0 to 3, with increased BDNF and platelet serotonin levels at 6 weeks, suggesting potential benefits for psychological suffering related to romantic stress.
Hypothalamic glutamate levels following serotonergic stimulation: a pilot study using 7-Tesla magnetic resonance spectroscopy in healthy volunteers.
A randomized, double-blind, placebo-controlled, two-way cross-over study in 12 healthy males examined the effects of 5-HTP on hypothalamic glutamate levels using 7-Tesla MRS. 5-HTP administration induced a significant decrease in Glx at 60 minutes and significant ACTH and cortisol release, suggesting activation of the HPA-axis.
Treatment of menopausal hot flashes with 5-hydroxytryptophan.
RCT of 5-HTP versus placebo in 24 postmenopausal women with frequent hot flashes. No significant effects of 150 mg/day 5-HTP on hot flash frequency were found, indicating no significant amelioration of menopausal hot flashes.
Faulty serotonin--DHEA interactions in autism: results of the 5-hydroxytryptophan challenge test.
The study examines plasma DHEA-S and the cortisol/DHEA-S ratio following administration of L-5-hydroxytryptophan (5-HTP) to 18 male autistic patients and 22 matched healthy controls. 5-HTP-induced DHEA-S responses were significantly higher in autistic patients than in controls, suggesting a disequilibrium in the serotonergic system in autism.
Pharmacology of rising oral doses of 5-hydroxytryptophan with carbidopa.
A double-blind, placebo-controlled, single rising dose, four-way crossover trial in 15 healthy male volunteers investigated the neuroendocrine dose-response relationship of 5-HTP combined with carbidopa. Dose-dependent increases in cortisol and prolactin concentrations were observed, with nausea and vomiting as frequent side effects, limiting the applicability of doses above 100 mg.
Enhanced tolerability of the 5-hydroxytryptophane challenge test combined with granisetron.
A randomized, double-blind, placebo-controlled, four-way crossover trial in 12 healthy male volunteers tested the 5-HTP/CBD challenge combined with anti-emetics granisetron and domperidone. Granisetron suppressed nausea and vomiting without affecting neuroendocrine response or pharmacokinetics, enhancing the test's clinical applicability.
Increase of urinary 5-hydroxyindoleacetic acid excretion but not serum chromogranin A following over-the-counter 5-hydroxytryptophan intake.
A randomized, double-blind, placebo-controlled crossover study investigated the effect of 5-HTP on urinary 5-HIAA excretion and serum CgA levels in 8 healthy subjects. 5-HTP intake increased urinary 5-HIAA excretion significantly but did not affect serum CgA levels.
Serotonergic disturbances in autistic disorder: L-5-hydroxytryptophan administration to autistic youngsters increases the blood concentrations of serotonin in patients but not in controls.
This study examines the effects of L-5-hydroxytryptophan (5-HTP) administration on blood serotonin levels in 18 autistic patients and 20 healthy controls. 5-HTP significantly increased serotonin levels in autistic patients but not in controls, suggesting differences in serotonin synthesis between the groups.
L -5-Hydroxytryptophan treatment of sleep terrors in children.
Open pharmacological trial testing L-5-hydroxytryptophan (L-5-HTP) on sleep terrors in 45 children. After 1 month, 93.5% of treated patients showed a positive response, and 83.9% were sleep terror-free after 6 months, compared to the comparison group with persistent episodes.
Placebo-controlled comparison of three dose-regimens of 5-hydroxytryptophan challenge test in healthy volunteers.
Placebo-controlled, randomized, four-way crossover study in 12 healthy male volunteers assessing pharmacokinetics and pharmacodynamics of 5-HTP with or without carbidopa. The regimen of 5-HTP 100 mg plus carbidopa significantly altered cortisol and prolactin levels and increased the elimination half-life and area under the curve, with some nausea reported.
L-5-hydroxytryptophan can prevent nociceptive disorders in man.
Prospective, long-term, placebo-controlled study showing that L-5-HTP can significantly decrease the occurrence of migraines, suggesting it may alter CNS abnormalities underlying migraine mechanisms.
Fluoxetine, but not tricyclic antidepressants, potentiates the 5-hydroxytryptophan-mediated increase in plasma cortisol and prolactin secretion in subjects with major depression or with obsessive compulsive disorder.
The study examined the effects of chronic treatment with fluoxetine or tricyclic antidepressants on L-5-hydroxytryptophan (L-5-HTP)-induced increases in plasma cortisol and prolactin concentrations in patients with major depression or OCD. L-5-HTP increased plasma cortisol and PRL levels, with significantly higher responses in fluoxetine-treated patients compared to tricyclic-treated or unmedicated patients.
Fibromyalgia and migraine, two faces of the same mechanism. Serotonin as the common clue for pathogenesis and therapy.
RCT comparing the efficacy of MAOIs-A/B with 5-HTP, 5-HTP alone, MAOIs-A/B alone, or amitriptyline in fibromyalgia sufferers. The combination of MAOIs with 5-HTP significantly improved fibromyalgia syndrome as measured by Visual Analogic Scale, while other treatments showed poorer benefits. The study suggests enhancing serotonergic and adrenergic transmission as a treatment strategy.
Double-blind study of 5-hydroxytryptophan versus placebo in the treatment of primary fibromyalgia syndrome.
A double-blind, placebo-controlled study of 5-hydroxytryptophan (5-HTP) in 50 patients with primary fibromyalgia syndrome. Clinical parameters significantly improved with 5-HTP treatment, with only mild and transient side-effects reported.
5-Hydroxytryptophan versus methysergide in the prophylaxis of migraine. Randomized clinical trial.
RCT comparing 5-hydroxytryptophan (5-HTP) and methysergide in 124 migraine patients. 5-HTP showed significant improvement in 71% of cases, particularly in reducing intensity and duration of attacks, with fewer side effects than methysergide.
Effect of 5-hydroxytryptophan on serum cortisol levels in major affective disorders. III. Effect of antidepressants and lithium carbonate.
The study investigated the effect of 5-hydroxytryptophan (5-HTP) on serum cortisol levels in patients with affective disorders. Administration of 200 mg 5-HTP orally increased serum cortisol levels. Lithium carbonate and MAO inhibitors augmented this increase, while tricyclic and second-generation antidepressants diminished it. The findings suggest differential effects of these treatments on serotonin receptor sensitivity.
Antidepressant potentiation of 5-hydroxytryptophan by L-deprenil in affective illness.
In a double-blind controlled study, 58 affectively ill patients were treated with combinations of L-Deprenil, L-5-HTP, and benzerazide. Patients receiving L-Deprenil plus L-5-HTP showed significantly greater clinical improvement in mood compared to placebo, with a correlation between mood improvement and platelet MAO inhibition.
[Problems in clinical testing of a psychotropic substance examplified by L-5-HTP-ester (author's transl)].
The study investigated the acute psychotropic effects of an i.v. injectable form of the serotonin-precursor L-5-hydroxytryptophan (Ro 3-5940). Challenges in clinical testing, including the use of self-rating scales and informed consent, were discussed.
Gut bacteria-derived 5-hydroxyindole is a potent stimulant of intestinal motility via its action on L-type calcium channels.
The study investigates the microbial conversion of 5-hydroxytryptophan (5-HTP) to 5-hydroxyindole (5-HI) and its effects on gut motility. Oral administration of 5-HTP leads to 5-HI production, which accelerates gut transit time in rats by activating L-type calcium channels on colonic smooth muscle cells.
5-HTP Decreases Goat Mammary Epithelial Cells Apoptosis through MAPK/ERK/Bcl-3 pathway.
The study explores the interaction among 5-HTP, MAPK, and Bcl-3 in goat mammary gland epithelial cell apoptosis. 5-HTP treatment decreased cell apoptosis and promoted phosphorylation of ERK1/2, suggesting that 5-HTP decreases GMEC apoptosis through the MAPK/ERK/Bcl-3 pathway.
Theoretical Study of 5-HTP. Potential New Drug Resulting from the Complexation of 5-HTP with ATP
Theoretical study using DFT calculations to explore the potential complexation of 5-HTP with ATP. The study computes molecular parameters and suggests the possible existence of a complex that may have properties of a new drug.
Effects of oral 5-hydroxy-tryptophan on energy intake and macronutrient selection in non-insulin dependent diabetic patients.
Double-blind, placebo-controlled study of 5-HTP in 25 overweight non-insulin dependent diabetic patients. 5-HTP reduced daily energy intake, carbohydrate and fat intake, and body weight, suggesting its potential to improve dietary compliance in diabetes.
L-5-hydroxytryptophan does not stimulate LH secretion directly from the pituitary in patients with gonadotrophin releasing hormone deficiency.
The study investigated whether 5-HTP amplifies LH secretion by enhancing the pituitary response to GnRH in patients with hypogonadotrophic hypogonadism. Results showed that 5-HTP did not significantly alter LH pulse amplitude, suggesting its effect is not due to enhancement of pituitary response but possibly due to action on the hypothalamus.
Brain 5-HT neurotransmission during paroxetine treatment.
The study investigated the effect of repeated paroxetine administration on cortisol responses to 5-HTP in healthy subjects and depressed patients. In healthy subjects, cortisol response increased after one week of paroxetine treatment but diminished after three weeks. In depressed patients, an increased cortisol response was observed after 8 weeks of treatment.
Blood and urine 5-hydroxytryptophan and 5-hydroxytryptamine levels after administration of two 5-hydroxytryptamine precursors in normal man.
Randomised cross-over study in six healthy male subjects receiving equimolar amounts of 5-HTP and glu-5-HTP. Marked increases in urinary 5-HTP and 5-HT excretion were observed after infusion of both compounds, without significant changes in blood 5-HT levels.
Effect of pindolol on the L-5-HTP-induced increase in plasma prolactin and cortisol concentrations in man.
The study examined the effect of pindolol on L-5-HTP-induced increases in cortisol and prolactin secretion in 12 normal male volunteers. Pretreatment with pindolol significantly inhibited the prolactin response but not the cortisol response to L-5-HTP. The findings suggest that L-5-HTP-induced prolactin secretion requires 5-HT1A receptor activation.
Effects of 5-hydroxytryptamine and 5-hydroxytryptophan infusion on the human cough reflex.
RCT investigating the effects of 5-HT and 5-HTP on the human cough reflex in 8 male volunteers. Both substances reduced cough responses to a chloride-deficient solution compared to saline control, but not to capsaicin. 5-HT increased heart rate transiently, while 5-HTP did not.
A comparison of the effects of two putative 5-hydroxytryptamine renal prodrugs in normal man.
Randomized, placebo-controlled, cross-over study in five healthy male volunteers comparing the effects of 5-HTP and glu-5-HTP. Both compounds increased urinary excretion of 5-HT, with 5-HTP showing greater extra-renal formation. Glu-5-HTP was significantly antinatriuretic, while 5-HTP increased plasma aldosterone. No significant changes in pulse rate or blood pressure were observed.
Eating behavior and adherence to dietary prescriptions in obese adult subjects treated with 5-hydroxytryptophan.
Double-blind RCT with 20 obese patients comparing 5-HTP (900 mg/d) to placebo over two 6-week periods. Significant weight loss, reduced carbohydrate intake, and early satiety were observed in 5-HTP-treated patients, suggesting 5-HTP may be safely used to treat obesity.
Effect of a serotonin precursor and uptake inhibitor in anxiety disorders; a double-blind comparison of 5-hydroxytryptophan, clomipramine and placebo.
A double-blind placebo-controlled study comparing 5-HTP and clomipramine in 45 patients with anxiety disorders. Clomipramine showed significant improvement on all rating scales, while 5-HTP showed moderate reduction in anxiety symptoms but did not affect depressive symptoms.
Neuroendocrine response to 5-hydroxytryptophan in seasonal affective disorder.
A double-blind study comparing placebo and 5-hydroxytryptophan (200 mg orally) in 10 patients with seasonal affective disorder and 10 controls. 5-HTP administration led to increased cortisol levels and decreased prolactin levels in both groups, with no significant changes in melatonin, growth hormone, blood pressure, or pulse rate.
Serotonin precursors in chronic primary headache. A double-blind cross-over study with L-5-hydroxytryptophan vs. placebo.
Double-blind cross-over study of 31 patients with chronic primary headache comparing L-5-HTP to placebo. L-5-HTP was more effective than placebo in reducing headache frequency and severity, but the difference was not statistically significant. Favourable responses were obtained in 48% of cases after two months of treatment. Side effects were mild and transient.
Clinical and polygraphic effects of d.1 5 HTP on narcolepsy-cataplexy.
Double-blind crossover RCT of 5-HTP (600 mg/day) vs placebo in 11 narcoleptic-cataplectic patients over 4 weeks. No change in daily cataplectic and narcoleptic attacks, but a trend toward decreased daytime sleep duration and a significant increase in nighttime sleep duration.
5-Hydroxytryptophan (5-HTP) and a MAOI (nialamide) in the treatment of depressions. A double-blind controlled study.
Double-blind controlled study in 30 hospitalized patients with endogenous depression comparing nialamide + l-5-HTP to nialamide alone. The combination treatment achieved fuller recovery and shorter onset delay, with less orthostatic hypotension.
Double-blind clinical trial of 5-hydroxytryptophan in a case of Lesch-Nyhan syndrome.
Double-blind clinical trial of 5-hydroxytryptophan (5-HTP) in a single case of Lesch-Nyhan syndrome. 5-HTP significantly reduced athetoid movement and had a sedative effect but did not improve mood or reduce self-mutilation.
5-Hydroxytryptophan (5-HTP): Natural Occurrence, Analysis, Biosynthesis, Biotechnology, Physiology and Toxicology
This narrative review covers the natural occurrence, analysis, biosynthesis, biotechnology, physiology, and toxicology of 5-HTP. It discusses the physiological effects of 5-HTP in the treatment of various conditions such as depression, anxiety, panic, sleep disorders, obesity, myoclonus, and serotonin syndrome, as well as its toxicity and potential impurities.
Effects of Serotonin and Slow-release 5-HTP on Gastrointestinal Motility in a Mouse Model of Depression.
The study investigated the effects of slow-release 5-HTP on gastrointestinal motility in a mouse model with a mutation analogous to a human depression-related mutation. Administration of 5-HTP SR restored serotonin levels in enteric neurons, normalized GI motility, and improved enteric epithelial growth in TPH2-R439H mice.
The Triple Combination Phentermine Plus 5-HTP/Carbidopa Leads to Greater Weight Loss, With Fewer Psychomotor Side Effects Than Each Drug Alone
Animal study investigating the effects of a triple combination of phentermine, 5-HTP, and carbidopa on weight loss and psychomotor side effects. The combination led to greater weight loss than each drug alone and partially reversed psychomotor side effects induced by phentermine.
5-Hydroxy-L-tryptophan suppresses food intake in food-deprived and stressed rats.
The study examined the effect of 5-HTP on food consumption in rats subjected to food deprivation and stress, finding that 5-HTP suppressed food intake in a dose-dependent manner, especially in the stress model. In humans, oral 5-HTP increased plasma 5-HTP levels significantly.
5-Hydroxytryptophan (5-HTP)
The paper discusses 5-Hydroxytryptophan (5-HTP) as a potential antidepressant through serotonergic mechanisms. It notes past FDA bans due to toxic reactions but states 5-HTP is now considered safe with current manufacturing standards. Limited research has been conducted since the 1980s, and new studies are recommended.
5-HTP efficacy and contraindications
The paper discusses the efficacy and contraindications of L-5-hydroxytryptophan (5-HTP) as a precursor to serotonin. It critiques exaggerated claims about its effectiveness for depression and suggests it may be contraindicated for some patients.
Positron emission tomography (PET) in neuroendocrine gastrointestinal tumors.
The study used PET to assess the uptake of 11C-5-HTP in patients with neuroendocrine tumors and liver metastases. It found high accumulation of 5-HTP in liver metastases, suggesting its potential use in visualizing serotonin-producing tumors and monitoring treatment effects.
The effect of serotonin precursors on alpha- and gamma-motoneuron activity.
The study examined the effects of 5-HT precursors, 5-HTP and tryptophan, on alpha- and gamma-motoneuron activity in spinal cats. 5-HTP increased motoneuron activity, effects reversed by 5-HT antagonists, suggesting mediation by 5-HT. Tryptophan alone had minimal effects unless pretreated with pargyline.
The indoleamine hypothesis of depression: an overview and pilot study.
This paper reviews the indoleamine hypothesis of depression and presents data on six patients with depression treated with L-5-HTP. The treatment was associated with a rise in CSF5-HIAA, but only two patients showed a decrease in depression ratings. 5-HTP also decreased urinary excretion of 17 hydroxycorticosteroids, suggesting a link between serotonin metabolism and the pituitary adrenal system.
THE EFFECTS OF 5-HYDROXYTRYPTOPHAN AND l-TRYPTOPHAN ON SPINAL SYNAPTIC ACTIVITY
The study investigated the effects of 5-hydroxytryptophan (5-HTP) and l-tryptophan on spinal synaptic activity in animals. 5-HTP increased monosynaptic spike height and decreased polysynaptic and dorsal root reflexes, with elevated 5-HT levels in the spinal cord. l-Tryptophan also increased monosynaptic spike height but had a moderate effect on polysynaptic and dorsal root reflexes.
A novel neurodevelopmental syndrome responsive to 5-hydroxytryptophan and carbidopa.
The paper reports on five boys with a neurodevelopmental syndrome characterized by motor delay and hypotonic-ataxic syndrome, responsive to treatment with 5-hydroxytryptophan and carbidopa. Treatment resulted in clinical improvement and normalization of serotonin metabolite levels in CSF and urine, suggesting a potential regulatory defect in serotonin production.
5-Hydroxytryptophan: a review of its antidepressant efficacy and adverse effects.
Review of studies on 5-hydroxytryptophan (5-HTP) as a serotonin precursor for depression treatment. Suggests antidepressant properties of 5-HTP, with relatively few adverse effects in depressed patients, though additional trials are needed.
An evaluation of the mechanism by which serotonergic activation depresses respiration.
The study investigates whether the depression of respiration by serotonergic agonists is due to peripheral or central nervous system effects. Systemic administration of 5-HTP and 5-MDMT in pargyline-treated animals suggests central penetration as the cause, with findings indicating central serotonergic neuron involvement.
In search of the mode of action of antidepressants: 5-HTP/tyrosine mixtures in depression.
The paper discusses the mode of action of antidepressants, focusing on the antidepressant properties of 5-HTP and tyrosine. It suggests that 5-HTP effects in depression are potentiated by tyrosine, supporting the hypothesis that activation of MA-ergic activity is linked to antidepressant activity.