Possible Interaction: Norepinephrine and Tryptophan

“If TRP depletion sufficiently reduced presynaptic 5-HT inhibition of NE function in PD patients, this could lead to a transient increase in NE function with accompanying increases in anxiety, blood pressure, and the NE metabolite 3-methoxy-4hydroxyphenylglycol (MHPG).”

“Recently we have shown that surplus dietary tryptophan TRP ) reduced the plasma concentrations of cortisol and noradrenaline in pigs.”

“ Norepinephrine and epinephrine, and to a lesser extent histamine, also increased W and decreased SWS and PS, whereas serotonin, dopamine and carbachol, a cholinergic agonist, had no effect.”

“SH rats, treated with the higher dose of tryptophan , also significantly reduced their urinary outputs of epinephrine and norepinephrine compared with SH controls, while both doses of tryptophan increased urinary outputs of dopamine significantly above that of SH controls.”

“These results show … dietary administration of tryptophan can reduce the elevated blood pressure of SH rats and support the possibility that … amino acid may act via its effect on the concentration of the neurohormones, norepinephrine and dopamine, in the diencephalon to regulate … binding of Ang II to its receptors.”

“Conversely, NE (1.0 microgram.kg-1.min-1) increased SVI 14%, MAP 29%, and TRP 26%, with no change in CI.”

“After PCS, an initial decrease at 7 days postoperatively of brain norepinephrine and blockade of the intracerebral metabolism of tryptophan were observed.”

“ Norepinephrine inhibits cortisol-mediated induction of hepatic tryptophan pyrrolase in rats.”