Synephrine, a Component of Evodiae Fructus, Constricts Isolated Rat Aorta via Adrenergic and Serotonergic Receptors

Abstract

We investigated the effects of Evodiae Fructus and synephrine, one of the components of Evodiae Fructus, on blood vessels. We found that Evodiae Fructus (1 × 10⁻⁶ – 3 × 10⁻⁴ g/mL) had constrictive effects on rat aorta. The vasoconstrictive effects of Evodiae Fructus were significantly inhibited by pretreatment with prazosin (adrenergic α₁-receptor antagonist), BRL15572 [5-hydroxytryptamine (5-HT)_1D antagonist], and ketanserin (5-HT_2A antagonist), but its vasoconstrictive effects were not inhibited by pretreatment with SB216641 (5-HT_1B antagonist) or propranolol (adrenergic β-receptor antagonist). These results suggest that Evodiae Fructus constricts rat aorta via adrenergic and serotonergic receptors. We also investigated the constrictive effects of synephrine on blood vessels. The vasoconstrictive effects of synephrine (1 × 10⁻⁷ – 3 × 10⁻⁵ mol/L) were significantly inhibited by pretreatment with prazosin, BRL15572, and ketanserin. However, its constrictive effects were not inhibited by pretreatment with SB216641 and propranolol. The pA₂ values of prazosin or ketanserin were nearly equal between Evodiae Fructus and synephrine. Because the constrictive effects of both Evodiae Fructus and synephrine were exerted via adrenergic α₁-receptors and serotonergic (5-HT_1D and 5-HT_2A) receptors, synephrine may be one of the important components in the constrictive effects of Evodiae Fructus.