Using the cannula inserting method, vasodilator responses to alpha 2-adrenoceptor agonists (clonidine, guanabenz, DJ7141 and xylazine) were investigated in isolated and perfused rat common carotid arteries. Alpha 2-adrenoceptor agonists dose-dependently induced a vasodilation in preparations preconstricted by noradrenaline. The potencies were in the order of clonidine greater than guanabenz greater than DJ-7141 greater than or equal to xylazine. Removal of the endothelium inhibited ACh-induced vasodilation, but not the alpha 2-agonist-induced dilation. Atropine treatment inhibited ACh-induced vasodilation, but not the alpha 2-agonist-induced dilation. Alpha 2-agonist-induced dilations were not modified by beta-blockade, which significantly suppressed isoprenaline-induced vasodilations. The potent alpha 2-adrenoceptor antagonist DG5128 did not influence the alpha 2-agonist-induced vasodilation. In preparations preconstricted by PGF2 alpha, clonidine and xylazine never induced a vasodilation, and clonidine frequently induced vasoconstrictions that were completely blocked by bunazosin. It is concluded that alpha 2-adrenoceptor agonist-induced vasodilation is independent from the existence of the endothelium, and that it is not related to vascular beta- and alpha 2-adrenoceptors and muscarinic receptors, suggesting that the alpha 2-adrenoceptor agonist-induced vasodilation is due to an antagonistic activity towards the vascular alpha 1-adrenoceptors.

1987-03-01·Biochemical pharmacology2区 · 医学

Effects of DJ-7141, a new α2-adrenoceptor agonist, on catecholamine secretion from isolated bovine adrenal medullary cells

2区 · 医学

Article

作者: Misbahuddin, Mir ; Ishimura, Yasuko ; Morita, Kyoji ; Oka, Motoo

The effects of a newly synthesized alpha 2-adrenoceptor agonist (an imidazole derivative, DJ-7141) on catecholamine secretion from isolated bovine adrenal medullary cells were examined. DJ-7141 did not affect basal catecholamine secretion, but inhibited catecholamine secretion induced by stimulation of the nicotinic ACh receptor. This inhibitory effect of DJ-7141 was less than that of clonidine, another alpha 2-agonist. DJ-7141 also inhibited [45Ca]2+ uptake by the cells induced by nicotinic stimulation. DJ-7141 did not affect catecholamine secretion induced by high K+ concentration. Its inhibitory effect on nicotine-induced catecholamine secretion was not restored by increase in either the nicotine or Ca2+ concentration of the medium, suggesting that it interfered with the coupling between nicotinic ACh receptor stimulation and Ca2+-channel activation. The inhibitory effect of DJ-7141 seemed to be independent of its effect on alpha 2-adrenoceptors, because its effect was not antagonized by the alpha 2-adrenoceptor antagonists yohimbine and DG-5128, which both had no effect on either basal or nicotine-induced catecholamine secretion.

1987-01-01·Japanese journal of pharmacology

Effects of DJ-7141, a new peripherally acting alpha-2 adrenoceptor agonist, on blood pressure and gastric acid output in rats : Evidence for the heterogeneity of alpha-2 adrenoceptors in different organs.

Article

作者: Yokotani, Kunihiko ; Osumi, Yoshitsugu

Effects of intravenously administered clonidine and DJ-7141 on blood pressure and gastric acid output were studied in anesthetized rats. Both drugs caused a dose-dependent increase in blood pressure. Clonidine-induced increases in the blood pressure were attenuated by yohimbine and prazosin. DJ-7141-induced increases in blood pressure were also attenuated by yohimbine, but were little affected even by a large dose of prazosin. Splanchnic nerve stimulation-induced increases in blood pressure were attenuated by clonidine and DJ-7141. The inhibitory effects of DJ-7141 exceeded those of clonidine. On the other hand, these agonists had no effect on exogenously applied norepinephrine-induced increases in blood pressure. Vagally stimulated gastric acid output was inhibited by small doses of clonidine and large doses of DJ-7141. Clonidine-induced inhibition of acid output was abolished by yohimbine (5 mg/kg), but not by prazosin (5 mg/kg). In contrast, the DJ-7141-induced inhibition of acid output was not affected by yohimbine (5 mg/kg), but was attenuated by a small dose of prazosin (0.1 mg/kg). These results indicate that DJ-7141 had no effect on alpha-2 adrenoceptors in gastric parasympathetic nerves. Furthermore, the alpha-2 adrenoceptors on parasympathetic nerves in the gastric wall are probably pharmacologically different from those on sympathetic nerves and blood vessels in rats.

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