Differential mechanisms of action of the trace amines octopamine, synephrine and tyramine on the porcine coronary and mesenteric artery

Figures

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  Figure 1. Chemical structures of the trace amines (tyramine, octopamine, and synephrine) and noradrenaline.

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  Figure 2. Initial cumulative-dose responses of trace amines and noradrenaline on isolated mesenteric artery. The amines shown are tyramine (● n = 6), synephrine (■, n = 6) and octopamine (▲, n = 6). The data are presented as percent of contraction to 60 mM potassium chloride (%KCl). Welch corrected unpaired t-test, *, p < 0.05 vs. tyramine; ^, p < 0.05 vs. synephrine.

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  Figure 3. (Left) Concentration-response curves of the porcine coronary artery to tyramine, octopamine and synephrine (n = 6–8). (Right) Concentration-response curves to noradrenaline in the absence of antagonists and in the presence of the β-adrenoceptor antagonist propranolol (1 M) and in the combined presence of propranolol (1 µM) and the α1-adrenoceptor antagonist prazosin (1 µM). Responses are expressed as a percentage of the contractile response to potassium chloride (60 mM). Student’s paired parametric t-test *p < 0.05 vs. the relaxation before addition of antagonists.

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  Figure 4. Concentration-response curves to tyramine (A,D), octopamine (B,E) and synephrine (C,F) in control tissues (○), mesenteric (A–C) and coronary arteries (D–F) previously depleted of neuronal NA (▪) using prolonged contact (60 mins) with a high concentration (3 mM) of tyramine. Data are means ± sem values from 6 to 24 experiments, expressed as a percentage of the contractile response to potassium chloride (60 mM). Student’s paired parametric t-test *p < 0.05 vs. control.

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  Figure 5. Concentration-response curves to trace amines in the absence (○) and presence of prazosin (1 µM, ■) in NA-depleted mesenteric arteries (A–C); and NA-depleted coronary arterial rings (D–F). Data are means ± sem (n = 5–7) values expressed as a percentage of the contractile response to potassium chloride (60 mM). Student’s paired parametric t-test *p < 0.05 vs control.

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  Figure 6. Concentration-response curves to tyramine (A,D), octopamine (B,E) and synephrine (C,F) in the absence (○) and presence of the TAAR-1 antagonist, EPPTB at 100 nM (■;A–C) or 100 µM (▲;D–F) in porcine coronary arterial rings. Data are means ± sem from 5 to 8 separate experiments, expressed as a percentage of the contractile response to potassium chloride (60 mM). Student’s paired parametric t-test *p < 0.05 vs. control, **p < 0.01 vs. control.