Amylin increases transport of tyrosine and tryptophan into the brain

Injection of amylin (diabetes-associated peptide) into the hypothalamus induces anorexia, increases brain metabolism of dopamine and serotonin and elevates brain level of tryptophan. When male Sprague-Dawley rats were treated with 50 mg/kg L-tryptophan and L-tyrosine ethyl ester 30 min prior to the intrahypothalamic injection of 2 micrograms amylin, brain tryptophan and tyrosine levels were selectively increased as compared to rats treated with amylin alone. Hypothalamic and striatal serotonin metabolism also appeared to be increased following the amino acid-amylin treatment combination. These results suggest that amylin may increase transport of tyrosine and tryptophan into the brain, and that the increased availability of tryptophan may contribute to increased serotonin turnover observed following intrahypothalamic amylin treatment.