Distribution and effects of intestinally administered [14C]-tyramine in cats, modified by monoamine oxidase inhibitors

[14C]‐β‐phenethylamine, its distribution after administration by various routes to cats, and the effects of monoamine oxidase inhibitors

“…A proportion of the instilled PEA was probably metabolized by intestinal MAO A, although blood concentrations of PEA following its i.d. administration were not increased by clorgyline pretreatment, despite a 66% inhibition of MAO A at the instillation site (see Garcha et al, 1983a).…”

“…This could account for its rapid absorption with a peak concentration in portal blood 5 to 10 min after intraduodenal instillation compared with one at 60-90min after i.d. tyramine (Garcha et al, 1983a) (Garcha et al, 1983a). The large concentrations of PEA and PAA in liver, jejunum or kidney, which taken alone would have implied 100% absorption of PEA, contrasted with much smaller concentrations in other tissues, such as skeletal muscle which contribute proportionately greater to body weight.…”

“…Several foods contain more than one amine (Marley & Blackwell, 1970) (Garcha et al, 1983a), again reflecting a greater role of the intestine in deaminating tyramine than PEA. MAO B constitutes 43% of the MAO activity in cats' intestine (Squires, 1972), yet blood concentrations of PEA were not significantly altered in cats pretreated with deprenyl.…”

“…This could be for a variety of reasons e.g. MAO B inhibition at the instillation site was only 33% with the dose of deprenyl cited (Garcha et al, 1983a); PEA can also serve as a type A, type B or dual substrate depending on the organ examined (Lyles & Callingham, 1973;Dial & Clarke, 1978), or on the substrate concentration. A proportion of the instilled PEA was probably metabolized by intestinal MAO A, although blood concentrations of PEA following its i.d.…”

“…Although less potent as a pressor agent than cats, revealed a dissimilar pattern of absorption, another dietary amine, tyramine, its ingestion in distribution and tissue concentrations compared to cheese could also have contributed in a minority ofthe tyramine. Indeed, since these tissue concentrations were substantially larger than those following identical doses of tyramine, P-phenethylamine emerges as potentially the most relevant to migraine of the three dietary amines examined, the others being histamine (Imrie et al, 1978) and tyramine (Garcha et al, 1983a). A preliminary account of the results has been communicated to the British Pharmacological Society (Garcha et al, 1983b).…”