5-Hydroxy-L-tryptophan

Diarrhea-predominant irritable bowel syndrome (IBS-D) is one of the most common diagnoses made by gastroenterologists. Current pharmacologic treatments for IBS-D include fiber supplements, antidiarrheal over-the-counter medications, probiotics, antispasmodics, antidepressants, and a 5-hydroxytryptophan 3 receptor antagonist. All of these options have limited efficacy in managing IBS-D. Rifaximin, a nonabsorbable antibiotic, has been evaluated in patients with IBS-D. In two randomized, double-blind, placebo-controlled phase III trials evaluating rifaximin 550 mg by mouth 3 times/day for 14 days, the primary efficacy end point was achieved by 9% more patients randomized to the rifaximin group compared with placebo (40.7% vs 31.7%, p<0.001, number needed to treat ~11). The primary efficacy end point was defined as the proportion of patients having adequate relief of global IBS symptoms for at least 2 of the 4 weeks during the primary follow-up period (weeks 3-6).

Neuroendocrine tumors (NETs) comprise a heterogeneous group of malignancies with a very variable clinical expression and progression. They present unique properties that are important to consider for radiological and nuclear imaging, such as APUD-characteristics (amine precursor uptake and dearboxylation), as well as the expression of somatostatin receptors. The most common localizations are the lungs, gastrointestinal tract and pancreas. The only curative treatment is surgery, but more than 50% present metastatic disease at the time of diagnosis. The systemic treatment includes chemotherapy and targeted agents, as well as peptide receptor radiotherapy. The diagnosis and follow-up of these tumors necessitate a large number of different imaging methods, such as CT, MRI, US, SRS and PET. Ultrasonography offers the possibility to take guided biopsies from different lesions. Somatostatin receptor scintigraphy was developed in the 1990s and nowadays presents the standard of care for NETs in most countries.

Drugs, notably SSRIs, that elevate brain extracellular 5-HT (5-HTExt) are antidepressants. Unfortunately, most patients fail to remit. Multipronged clinical evidence suggests that elevating 5-HTExt beyond the SSRI effect enhances antidepressant efficacy, but previous such drug strategies had prohibitive limitations. In humans, adjunct treatment with the 5-HT precursor 5-hydroxytryptophan (5-HTP) elevates 5-HTExt beyond the SSRI effect. Small pilot trials suggest that adjunct 5-HTP can confer antidepressant response in treatment-resistant depression (TRD). However, sustained, stable 5-HTExt elevation is required for antidepressant effect; therefore, the rapid absorption and elimination of standard 5-HTP immediate release (IR) likely curtail 5-HTP IR's antidepressant potential. Slow-release (SR) drug delivery can crucially improve efficacy and safety of rapidly absorbed and eliminated compounds. Here we tested in mice the hypothesis that SR delivery will substantially improve 5-HTP's drug properties, by minimizing adverse effects and securing sustained 5-HTExt elevation beyond the SSRI effect.

Substantial evidence supports the neurochemical vulnerability to lead (Pb) as one of the most potent neurotoxic heavy metals. In the present study, we aimed to assess: (i) The subcommissural organ (SCO) responsiveness as a secretory circumventricular organ to chronic and acute Pb intoxication together with its serotoninergic innervation. (ii) The possible restorative effect of curcumin against Pb intoxication under the same pathological conditions. We used immunohistochemistry with antibodies against Reissner's fiber and serotonin [5-hydroxytryptophan (5-HT)] in Wistar rats following chronic as well as acute Pb administration, respectively, at 25 mg/kg intraperitoneally for 3 days and 0.3% in drinking water from the intrauterine stage until 2 months of adult age. Our data showed a significant decrease in Reissner's fiber material immunoreactivity concomitant with an overall increased 5-HT innervation of the SCO and the ventricular borders.