Sw,-Severe hypertension has been reported in patients treated with monomine oxidase inhibitors after eating cheese, beans, or certain yeast extracts (Blackwell, 1963; Blackwell, Marley & Mabbitt, 1965). The tyramine content of these foods is considered to be the principal pressor substance (Blackwell & Mabbit, 1965; Horwitz, Lovenberg, Engelman & Sjoerdsma, 1964). I now report the influence of monoamine oxidase inhibition on the noradrenalinereleasing effect of tyramine in rats. Adult Wistar male albino rats, 200 to 300 g, were given intraperitoneally pargyline 80 mg/kg. Twelve hr after this treatment the rats were deprived of food and 24 hr after the drug they were given different doses of tyramine by mouth. Four hr after the last treatment the rats were killed and their hearts were analysed for noradrenaline fluorornetrically (Brodie, Dablac & Costa, 1966). Control animals fasting for 12 hr received tyramine only. The results (Table 1) demonstrate that the monoamine oxidase inhibitor potentiated the effect of tyramine in depleting noradrenaline and indicate that the enhancement of the pressor effects of tyramine by mouth (Tedeschi & Fellows, 1964) is caused by an increased release of peripheral noradrenaline.
[1]
G. Gessa,et al.
Interaction of desmethylimipramine (DMI) with the adrenergic and NE releasing actions of tyramine, α-methyl-m-tyramine, and metaraminol☆
,
1966
.
[2]
H. Behnke.
MANAGEMENT OF POLYCYTHAEMIA VERA.
,
1965,
Lancet.
[3]
W. Lovenberg,et al.
Monoamine Oxidase Inhibitors, Tyramine, and Cheese
,
1964
.
[4]
D. H. Tedeschi,et al.
Monoamine Oxidase Inhibitors: Augmentation of Pressor Effects of Peroral Tyramine
,
1964,
Science.
[5]
B. Blackwell.
HYPERTENSIVE CRISIS DUE TO MONOAMINE-OXIDASE INHIBITORS.
,
1963,
Lancet.