We have recently suggested that atypical β-adrenoceptors are present in guinea pig gastric fundus and duodenum. In the present study, we have shown that SR59230A (3-(2-ethylphenoxy)-1-[(1S)-1,2,3,4-tetrahydronaphth-1-ylamino]-(2S)- 2-propanol oxalate), a selective β3-adrenoceptor antagonist, possesses agonistic activities at atypical β-adrenoceptors in these tissues. SR59230A caused concentration-dependent relaxations. However, (±)-propranolol (1 μM) did not affect SR59230A-induced relaxations. Pretreatment of with a combination of (±)-propranolol (1 μM) and the non-selective β1-, β2-, β3- and β4-adrenoceptor antagonist, (±)-bupranolol (30 μM), significantly antagonized the relaxant effects induced by SR59230A. The results clearly indicate that SR59230A acts as an atypical β-adrenoceptor agonist on guinea pig gastric fundus and duodenum. © 2001 Elsevier Science B.V.
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