DJ-7141, a new alpha-2 agonist with only a mild hypotensive action

Pharmacological profiles of a novel alpha 1-adrenoceptor agonist, PNO-49B, at alpha 1-adrenoceptor subtypes

The effects of a newly synthesized compound, PNO-49B, (R)-(-)-3'-(2-amino-1-hydroxyethyl)-4'-fluoromethanesulfonanilide hydrochloride, on alpha 1-adrenoceptor subtypes were examined in various tissues in which the following distribution of alpha 1-adrenoceptor subtypes has been suggested: dog carotid artery (alpha 1B), dog mesenteric artery (alpha 1N), rabbit thoracic aorta (alpha 1B + alpha 1L), rat liver (alpha 1B), rat vas deferens (alpha 1A + alpha 1L), rat cerebral cortex (alpha 1A + alpha 1B) and rat thoracic aorta (controversial subtype). PNO-49B (0.1-100 microM) produced concentration-dependent contractions in dog mesenteric artery, rabbit thoracic aorta, rat thoracic aorta and rat vas deferens; and the maximal amplitudes of contraction were almost the same as or slightly less than those of noradrenaline. By contrast, the maximal response to PNO-49B in dog carotid artery was markedly smaller than the response to noradrenaline. In rabbit thoracic aorta, the contractile response to PNO-49B was not affected by inactivation of the alpha 1B subtype with chloroethylclonidine (CEC), although the response to noradrenaline was attenuated by that treatment. The dissociation constants (KA) of PNO-49B were not different among the rat thoracic aorta, dog carotid and mesenteric arteries and rabbit thoracic aorta (CEC-pretreated). The contractile responses to PNO-49B were inhibited competitively by prazosin, HV723 (alpha-ethyl-3,4,5-trimethoxy-alpha-(3-((2-(2-methoxyphenoxy)-ethyl)- amino(propyl)benzeneacetonitrile fumarate) and by WB4101 (2-(2,6-dimethoxyphenoxyethyl)-aminomethyl-1,4- benzodioxane).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of DJ-7141, a new alpha 2-adrenoceptor agonist, on catecholamine secretion from isolated bovine adrenal medullary cells

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.