Stahl's Essential Psychopharmacology by Stahl Stephen M

Author:Stahl, Stephen M. [Stahl, Stephen M.]
Language: eng
Format: epub, pdf
Publisher: Cambridge University Press
Published: 2013-04-11T00:00:00+00:00

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Figure 7-54. Tyramine increases norepinephrine release. Tyramine is an amine present in various foods, including cheese. Indicated in this figure is how a high-tyramine meal (40 mg, depicted here as cheese) acts to increase the release of norepinephrine (NE) (1). However, in normal circumstances the enzyme monoamine oxidase A (MAO-A) readily destroys the excess NE released by tyramine (2), and no harm is done (i.e., no vasoconstriction or elevation in blood pressure).

Figure 7-55. Inhibition of monoamine oxidase A (MAO-A) and tyramine. Here tyramine is releasing norepinephrine (NE) just as shown in Figure 7-54 (1). However, this time MAO-A is also being inhibited by an irreversible MAO-A inhibitor. This results in MAO-A stopping its destruction of NE (2). As indicated in Figure 7-51, such MAO-A inhibition in itself causes accumulation of NE. When MAO-A inhibition is taking place in the presence of tyramine, the combination can lead to a very large accumulation of NE (3). Such a great NE accumulation can lead to excessive stimulation of postsynaptic adrenergic receptors (3) and therefore dangerous vasoconstriction and elevation of blood pressure.

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