ISSN:
1432-1912
Keywords:
Key words β-adrenoceptors
;
β adrenoceptor antagonists
;
Celiprolol
;
Rat
;
Blood pressure
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Celiprolol is a β-adrenoceptor antagonist which has desirable ancillary properties since it is relatively cardioselective and can exert direct vasodilator and bronchodilator effects. Here agonist and antagonist effects of celiprolol at cardiac β1- and vascular β2-adrenoceptors were determined under in vivo conditions in the rat. All experiments were carried out in catecholamine-depleted, pentobarbital anesthetized and vagotomized rats, placed under artificial respiration. I.v. administrations were madevia the femoral vein. Blood pressure was measured from the cannulated right carotid artery and heart rate was recorded with a cardiotachometer. Celiprolol (10 µg/kg to 1 mg/kg i.v.) produced dose-related increases in heart rate and decreases in mean carotid artery blood pressure which were of longer duration than those mediated by standard agonists of β1-(isoprenaline) or β2-(salbutamol) adrenoceptors respectively. Although the maximal increase in heart rate by celiprolol (110±4 beats/min, n=7) was approximately half that of isoprenaline (198±1 beats/min, n=5), isoprenaline acted at doses 200-fold lower than celiprolol. Betaxolol (0.03-0.3 mg/kg i.v.), a β1-adrenoceptor antagonist, inhibited strongly and with similar potency the tachycardic effects of celiprolol (DR10 = 45 µg/kg i.v.) as well as isoprenaline (DR10 = 45 µg/kg i.v.). On the other hand, the hypotensive effects of celiprolol and salbutamol were antagonized markedly and with similar potency by ICI118,551, a relatively selective β2-adrenoceptor antagonist (DR10 = 15 and 25 µg/kg i.v. respectively). In rats pretreated with celiprolol (0.03 to 0.3 mg/kg i.v.), the heart rate dose-response curves to isoprenaline were shifted to the right of those determined in matched groups of vehicle-pretreated animals. In this respect, celiprolol was half as potent as betaxolol in blocking cardiac β1-adrenoceptors. Furthermore, celiprolol also antagonized the hypotensive effects of salbutamol, but, in this respect, celiprolol was 90-fold less potent than ICI 118,551. In conclusion, these results clearly indicate that celiprolol has the ability of stimulating and blocking not only cardiac β1- but also vascular β2-adrenoceptors. The effects on cardiac β1-adrenoceptors as well as the agonism of β2-adrenoceptors are produced by similar doses of celiprolol. These doses are notably lower than those necessary to block β2-adrenoceptors. Thus, this pharmacological profile, which has also been demonstrated in humans, indicates that celiprolol is a modulator of cardiac β1-adrenoceptors with vascular β2-adrenoceptor agonist properties.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/PL00005001
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