That view has led some clinicians to try oxytocin as a treatment for psychiatric conditions such as autism spectrum disorder. But the early trials have had mixed results, and scientists are now seeking a deeper understanding of oxytocin and how it works in the brain. Researchers such as Froemke are showing that the hormone boosts neuronal signals in a way that could accentuate socially relevant input such as distress calls or possibly facial expressions. And clinical researchers are starting a wave of more ambitious trials to test whether oxytocin can help some types of autism.
The short half-life (<2h) of 5-HTP may inherently limit the therapeutic potential of 5-HTP, as the systemic 5-HTP exposure levels will fluctuate substantially, even with relatively frequent dosing. Such exposure fluctuations are usually associated with increased adverse event burden, resulting from Cmax drug spikes, and decreased clinical efficacy resulting from sub-therapeutic exposure for large parts of the day. It has been proposed that 5-HTP dosage forms achieving prolonged delivery would be more effective, as is generally the situation with short-acting active pharmaceutical ingredients.
So far, few studies have definitively linked autism to problems in oxytocin signalling. Some of the clearest evidence emerged in February, from a team led by neurogeneticist Daniel Geschwind of the University of California, Los Angeles. The group showed that mice that lacked a working copy of the Cntnap2 gene — which has been implicated in a small subset of human autism cases — had fewer oxytocin-containing neurons in the hypothalamus and socialized less with other mice than did control mice15. After receiving doses of oxytocin every day for two weeks, the mice behaved normally again. “Until this, there was no evidence that there was a subtype of autism that had to do with oxytocin deficits,” Geschwind says.
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.
Nolen, W. A., van de Putte, J. J., Dijken, W. A., Kamp, J. S., Blansjaar, B. A., Kramer, H. J., and Haffmans, J. Treatment strategy in depression. II. MAO inhibitors in depression resistant to cyclic antidepressants: two controlled crossover studies with tranylcypromine versus L-5-hydroxytryptophan and nomifensine. Acta Psychiatr.Scand 1988;78(6):676-683. View abstract.
To explore whether Tβ4 peptide-induced anti-inflammatory and anti-osteoclastogenesis were dependent on the up-regulation of Wnt5a, the effects of recombinant human (rh) Wnt5a (500 ng/mL) and Wnt5a-specific siRNA were assessed. Pretreatment of Wnt5a siRNA reversed the inhibitory effects of Tβ4 peptide on H2O2-induced iNOS and COX-2 expressions, NO and PGE2 productions, osteoclastogenic cytokines, and RANKL expression (Fig 10A–10E). In contrast, pretreatment with rhWnt5a enhanced the anti-inflammatory effects of Tβ4 peptide whereas control siRNA showed no effect on PDLCs. In accordance with anti-inflammatory results, Tβ4 peptide-suppressed osteoclast number and TRAP activity in BMM cells were reversed by exogenous treatment with Wnt5a siRNA but enhanced by rh-Wnt5a (Fig 11A–11C).
The first time Ditzen and her colleagues did this experiment they found that for both men and women oxytocin improved communication and lowered cortisol, a stress hormone. But in a recent study published in Social Cognitive and Affective Neuroscience, Ditzen and her colleagues measured salivary alpha-amylase (sAA)—an enzyme tied specifically to social stress—and found that men and women responded differently. Women who got oxytocin showed a decrease in sAA whereas men showed an increase and reported feeling more intense emotions. Counterintuitively, these men were also better at communication during conflict: they smiled more, had more eye-contact and were more open about their feelings. These behaviors are essential for peaceful conflict resolution.
“Ultimately you’re body is going to down-regulate the enzymes needed to convert the tyrosine/l-phenylalanine into dopamine and norepinephrine; this also counts for 5 -htp being converted into serotonin. As far as I’m aware when simply supplementing amino acids to improve neurotransmitter prevalence in the brain, tolerance will build very rapidly within a one week to two week period (from personal experience). Not saying it’s not viable to help out with mood when used sparingly, just saying there’s most likely better ways for continued treatment.”
5-HTP (5-Hydroxytryptophan) is a chemical by-product of the protein building block L-tryptophan. It is also produced commercially from the seeds of an African plant known as Griffonia simplicifolia 5-HTP is used for sleep disorders such as insomnia, depression, anxiety, migraine and tension-type headaches, fibromyalgia, obesity, premenstrual syndrome (PMS), premenstrual dysphoric disorder (PMDD), attention deficit-hyperactivity disorder (ADHD), seizure disorder, and Parkinson's disease..
Oral 5-HTP results in an increase in urinary 5-HIAA, a serotonin metabolite, indicating that 5-HTP is peripherally metabolized to serotonin, which is then metabolized. This might cause a false positive test in tests looking for carcinoid syndrome. Due to the conversion of 5-HTP into serotonin by the liver, there could be a risk of heart valve disease from serotonin's effect on the heart, as based on preclinical findings. However, 5-HTP has not been associated with cardiac toxicity in humans.