Possible Interaction: Dihydroxyphenylalanine and Melatonin

“ Melatonin treatment significantly reduced the mRNA expression of catecholamine synthases, including the rate-limiting enzyme tyrosine hydroxylase (Th), 3,4-dihydroxyphenylalanine decarboxylase and dopamine-β-hydroxylase expressed in PC12 cells.”

“When L‐DOPA in small doses (5–8 mg/kg) failed to affect MPTP‐induced akinesia or catalepsy, co‐administration of melatonin with L‐DOPA attenuated these behaviors.”

“ Melatonin treatment significantly attenuated both the l‐DOPA and MPTP‐induced increases in the levels of striatal 6‐OHDA, and protected against striatal DA depletion caused by the neurotoxin.”

“It is evident that 5-HTP and L-DOPA given at the interval of 8h, as well as melatonin , are potent inhibitors of gonadal development, and the gonado stimulatory effect of the 12-h temporal relationship of the neurotransmitter precursors is masked by the inhibitory effect of melatonin.”

“Co‐infusion of N‐acetylcysteine (100 μm) or melatonin (50 μm) increased l‐DOPA (up to 151‐ and 246‐fold, respectively) and decreased l‐DOPA‐SQ (by about 53% and 87%, respectively) dialysate concentrations.”

“These findings demonstrate that endogenous melatonin protects exogenous l‐DOPA from autoxidation in the extracellular compartment of the striatum of freely moving rats; moreover, systemic co‐administration of melatonin with l‐DOPA markedly increases striatal l‐DOPA bioavailability in control as well as in melatonin‐depleted rats.”

“In addition to β‐adrenergic receptor agonists, L‐dopa and dopamine have been also shown to activate the production of melatonin and its synthesizing enzyme, serotonin N‐acetyltransferase.”