The in vivo examination of the irreversible beta-adrenoceptor antagonist Ro 03-7894 on cardiac rate and contractility.
1. Two benzofuran-2-ethanolamines Ro 03-5255 (1-(5-acetylamino-benzofuran-2-yl)-1-hydroxy-2-isopropylaminoethane) and Ro 03-7894 (1-(5-chloracetyl aminobenzofuran-2-yl)-1-hydroxy-2-isopropylaminoethane) which had previously been shown to exhibit respectively competitive and irreversible beta-adrenoceptor antagonism in guinea-pig isolated atria, were compared in vivo using isoprenaline-induced tachycardia of anaesthetized guinea-pigs and heart rate and contractility (dp/dtmax) of open-chest anaesthetized guinea-pigs and of conscious cats. 2. In urethane-anaesthetized guinea-pigs doses of 3 mg/kg, s.c. of both antagonists produced significant blockade of the rate response to an 80% of maximum dose of isoprenaline after 4 h. In other experiments, guinea-pigs were pretreated with the antagonists and the responses to isoprenaline were then monitored. The slopes of the dose-response curves to isoprenaline were depressed for up to 24 h by Ro 03-7894 but this was not so with Ro 03-5255. 3. In conscious cats the course of blockade by Ro 03-7894 was followed in the same animals and was still evident after 48 h. In contrast, the beta-adrenoceptor blockage produced by Ro 03-5255 was not evident 24 h after administration. 4. The persistence of blockade by Ro 03-7894 was consistent with the irreversible mode of action demonstrated in vitro.
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D001572:Benzofurans / Q000494:pharmacology*; D002415:Cats; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004983:Ethanolamines / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D006339:Heart Rate / Q000187:drug effects*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D013997:Time Factors
D000319:Adrenergic beta-Antagonists; D001572:Benzofurans; D004983:Ethanolamines; C018430:Ro 03-7894; D007545:Isoproterenol