Chromium treatment decreases the sensitivity of 5-HT2A receptors

Rationale: Recent case series suggest that chromium picolinate in doses of 400 mug daily may have antidepressant properties, perhaps through increasing the peripheral availability of tryptophan for brain serotonin (5-HT) synthesis. Objectives: To determine the effects of chromium treatment on plasma tryptophan availability and on brain 5-HT function in human and animal models. Methods: We studied the effects of short-term chromium supplementation on plasma concentrations of tryptophan and other large neutral amino acids. Brain 5-HT function was assessed by measuring the corticosterone/cortisol response to the 5-HT precursor, 5-hydroxy-tryptophan (5-HTP), a response believed to be mediated via indirect activation of 5-HT2A receptors. Results: In rats. chromium increased peripheral and central tryptophan availability and elevated brain 5-HT content. Changes in peripheral tryptophan availability were not seen in humans but in both rats and humans. chromium lowered the cortisol response to challenge with 5-HTP. Conclusions: Chromium can modify brain 5-HT function in humans and animals. perhaps by altering the sensitivity of central 5-HT2A receptors.