ISSN:
1474-8673
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Chemistry and Pharmacology
,
Medicine
Notes:
Summary 1 The agonistic and antagonistic effects of labetalol, the α1- and β-adrenoceptor antagonist, were studied on β3-adrenoceptors in the guinea-pig gastric fundus. 2 Labetalol caused a concentration-dependent relaxation with a pD2 value of 5.58 ± 0.09 and an intrinsic activity of 0.64 ± 0.06, which was not affected by pretreatment with both the selective β1-adrenoceptor antagonist, (±)-atenolol (100 μM), and the selective β2-adrenoceptor antagonist, (±)-butoxamine (100 μM). 3 However, the non-selective β1-, β2- and β3-adrenoceptor antagonist, (±)-bupranolol (3–30 μM), shifted the concentration–response curve of labetalol to the right (pA2 value=5.97 ± 0.08). 4 In the presence of (±)-atenolol (100 μM) and (±)-butoxamine (100 μM), relaxations to catecholamines [(−)-isoprenaline, (−)-noradrenaline and (−)-adrenaline], to the selective β3-adrenoceptor agonist, BRL37344, and to the non-conventional partial β3-adrenoceptor agonist, (±)-CGP12177A, were weakly antagonized by labetalol (10 μM). 5 These results indicate that labetalol, the arylethanolamine, acts as a partial agonist on β3-adrenoceptors in the guinea-pig gastric fundus.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1046/j.1474-8673.2002.00239.x
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