Tyramine is an indirectly acting sympathomimetic amine that releases norepinephrine from presynaptic nerve terminals.

Tyramine is an indirectly acting sympathomimetic amine that releases norepinephrine from presynaptic nerve terminals[1]. Tyramine potentiates the postsynaptic inhibitory effects of norepinephrine on the firing of cortical neurones in the rat[2]. Although tyramine exists in three isomerie forms, the orthoisomer and metaisomers are present in very low concentrations and it is the paraisomer that is implied when reference is made to tyramine. The tyramines are generally present in nanogram/gram concentrations in brain tissue, but they have a very rapid turnover. The CNS role of tyramine is unclear, it has been suggested that it is involved in the modulation of dopamine synthesis and may also regulate norepinephrine turnover[3].

[1]. Harrison WM, et al. The tyramine challenge test as a marker for melancholia. Arch Gen Psychiatry. 1984 Jul;41(7):681-5. [2]. BURN JH, et al. The action of sympathomimetic amines in animals treated with reserpine. J Physiol. 1958 Dec 4;144(2):314-36. [3]. Juorio AV, et al. A possible role for tyramines in brain function and some mental disorders. Gen Pharmacol. 1982;13(3):181-3.