Supplements haven't been tested for safety and due to the fact that dietary supplements are largely unregulated, the content of some products may differ from what is specified on the product label. Also keep in mind that the safety of supplements in pregnant women, nursing mothers, children, and those with medical conditions or who are taking medications has not been established. You can get tips on using supplements, but if you're considering the use of 5-HTP supplements, talk with your primary care provider first. Self-treating a condition and avoiding or delaying standard care may have serious consequences.
In a landmark 1979 study3, Cort Pedersen and Arthur Prange at the University of North Carolina in Chapel Hill showed that giving oxytocin to virgin rats could trigger maternal behaviours: the animals would build nests, lick or crouch over unfamiliar pups and even return lost pups to the nest. Researchers went on to show that oxytocin signalling in the brains of prairie voles (Microtus ochrogaster) helps the animals to form lifelong pair bonds4 — a rarity among mammals. In 2012, researchers even found a version of oxytocin in the tiny roundworm Caenorhabditis elegans, where it helps the animals find and recognize mates5.

Moreover, Tβ4 concentration revealed wide variability, and it decreased in the gingival crevicular fluid (GCF) as periodontal disease progressed [19]. In contrast, Tβ4 mRNA expression was 3.76 fold higher in periodontitis-affected gingival tissue, compared with healthy individuals’ tissue obtained from public microarray data (GEO assession: GSE 23586) [20]. However, the Tβ4 mRNA level did not change in the periodontal-diseased gingival tissue (arbitrary units; 6.249) when compared with healthy tissue (arbitrary units; 6.242) (GEO assession: GSE 10334) [21]. Although Tβ4 exerts anti-inflammatory effects in vivo and in vitro, the precise role of Tβ4 in the inflammatory response remains unclear.

For example, when a mother is nursing her baby, that stimulation from the breast is going into the brain and causing those oxytocin neurons to fire and release oxytocin directly into the brain. That's much more powerful than what happens with a nasal spray. So I think that, you know, in the future, we may have these drugs that can, in a very potent way, tap into this oxytocin system to treat many different kinds of disorders.

Evidence for this role of oxytocin come from two types of experiments. First, infusion of oxytocin into the ventricles of the brain of virgin rats or non-pregnant sheep rapidly induces maternal behavior. Second, administration into the brain of antibodies that neutralize oxytocin or of oxytocin antagonists will prevent mother rats from accepting their pups. Other studies support the contention that this behavioral effect of oxytocin is broadly applicable among mammals.
Cells that line blood vessels (endothelial cells), taken from human umbilical chord veins, were grown in culture and the layer of cells subjected to a scratch wound. Cultures were then treated with Tb4 or kept in growth medium without Tb4. When examined four hours later, Tb4 treatment attracted cells to migrate into the wound and accelerated their movement, showing it is a chemoattractant. Cell migration was four to six times faster in the presence of Tb4 compared to the migration of untreated cells. Tb4 also hastened wound closure and increased the production of enzymes, called metalloproteases, that could pave the way for angiogenesis by breaking down barrier membranes and facilitating the invasion of new cells to the needy area, to form new vessels. Other experiments showed Tb4 acts in vivo. When endothelial cells were implanted under the skin in a gel supplemented with Tb4, the cells formed vessel-like structures containing red blood cells, indicating the ability to stimulate angiogenesis in the animals.
Cells were incubated with 200 μM H2O2 for indicated times (A). Cells were pretreated with indicated concentrations of Tβ4 peptide (0.1–5 μg/mL) for 2 hours and then incubated with 200 μM H2O2 for 60 minutes (B). Data were representative of three independent experiments. The bar graph shows the fold increase in protein expression compared with control cells * Statistically significant differences compared with the control, p<0.05. # Statistically significant difference compared with the H2O2—treated group.
Serotonin appears to be associated with panic attacks. Although studies that have used tryptophan depletion techniques in humans do not necessarily induce a panic attack[34][35][36] it appears it may sensitize the body by an increase in neurovegetative panic symptoms and increased anxiety[37] which suggests that serotonin is protective against panic attacks, at least acutely.[38][39] A study in 24 unmedicated panic disorder patients and normal participants given 200mg 5-HTP prior to a 35% CO2 test (used to induce a panic attack-like response) noted that the test was able to induce panic attack in both panic disorder patients and normal persons and that 200mg 5-HTP was protective in both conditions but to a greater degree in persons suffering from panic disorders.[40] This has been replicated with cholecystokinin-4 induced panic attack with 200mg 5-HTP in otherwise healthy persons.[41]

Myocardial infarction and heart failure are severe causes for death in humans. Extracellular nucleotides (ATP and ADP) released at the site of myocardial damage induce thrombosis, apoptosis and necrosis. ENTPD1 (ectonucleoside triphosphate diphosphohydrolase 1, CD39) rapidly hydrolyzes ATP and ADP to AMP. An in vivo myocardial ischemia/reperfusion injury test in transgenic mice expressing human CD39 resulted in a decrease of the infarct size. The same transgene including the human CD39 cDNA driven by the murine MHC class I gene H-2Kb promoter was used for the generation of transgenic pigs via SCNT. Expression of human CD39 was detected on circulating blood cells and in myocardial tissue of the transgenic animals. After in vivo induction of myocardial ischemia/reperfusion injury, a reduction of the myocardial injury analogous to the results in the transgenic mice was found (Wheeler et al., 2012).
Tb4 has other effects that are needed in healing and repair of damaged tissue. It is a chemo-attractant for cells, stimulates new blood vessel growth (angiogenesis), downregulates cytokines and reduces inflammation, thus protecting newly formed tissue from damaging inflammatory events. Tb4 has been shown to reduce free radical levels (with similar efficiency as superoxide dismutase), decrease lipid peroxidation, inhibit interleukin 1 and other cytokines, and decrease inflammatory thromboxane (TxB2) and prostaglandin (PGF2 alpha).
Oxytocin and vasopressin are the only known hormones released by the human posterior pituitary gland to act at a distance. However, oxytocin neurons make other peptides, including corticotropin-releasing hormone and dynorphin, for example, that act locally. The magnocellular neurosecretory cells that make oxytocin are adjacent to magnocellular neurosecretory cells that make vasopressin. These are large neuroendocrine neurons which are excitable and can generate action potentials.[124]
For depression: Most commonly, 150-800 mg daily is taken for 2-6 weeks. These doses are sometimes divided up and administered as 50 mg to 100 mg three times a day. Sometimes the dose starts out low and steadily increases every 1-2 weeks until a target dose is reached. Less commonly, higher doses are used. In one study, the dose is steadily increased up to 3 grams per day.
When combined with antidepressants of the MAOI or SSRI class, very high parenteral doses of 5-HTP can cause acute serotonin syndrome in rats.[23][24] It is unclear if such findings have clinical relevance, as most drugs will cause serious adverse events or death in rodents at very high doses. In humans 5-HTP has never been clinically associated with serotonin syndrome, although 5-HTP can precipitate mania when added to an MAOI.[25]