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  • 1
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 522 (1988), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 335 (1987), S. 344-350 
    ISSN: 1432-1912
    Keywords: Glucagon ; Rat regional haemodynamics ; Gastrointestinal blood flow ; Intrasplenic administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to determine whether or not glucagon released from the pancreas might have local vascular effects, the actions upon regional haemodynamics in the anaesthetised rat of two doses of glucagon (2 and 10 μg kg−1 min−1) infused intrasplenically (and thus into the portal vein) were compared with those of a single dose (2 μg kg−1 min−1) infused i. v. Infusion of glucagon i. v. produced a significantly increased heart rate (by 6%) and cardiac output (by 23%) in the experimental animals compared to those receiving saline by the same route. Total peripheral resistance fell by 24%. A greater proportion of the cardiac output passed to the coronary and renal vascular beds and blood flow was increased in the spleen, testes, pectoral skeletal muscle, stomach and small intestine as well as the heart and kidneys. The lower dose infused intrasplenically had no significant effect on cardiac output or total peripheral resistance but significantly increased the proportion of cardiac output passing both to the stomach and the small intestine such that the percentage of cardiac output flowing through the portal vein increased from 19.1 ± 1.1% to 23.8 ± 1.7%. Intrasplenic infusion of 10 μg kg−1 min−1 significantly increased cardiac output (by 29%) but reduced total peripheral resistance by 37%. Greater fractions of the cardiac output were received by the spleen, small intestine and epididymides. Blood flow was increased in these organs and the skin, kidneys, stomach, large intestine and the mesentery. It is concluded that pharmacologically effective amounts of glucagon only passed into the systemic circulation with the higher dose infused intrasplenically. Thus the redistribution of cardiac output in favour of the splanchnic bed with the lower dose of glucagon infused into the portal region is most likely the result of local mechanisms rather than a direct effect of the hormone on the inflow vasculature resulting from recirculation.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1912
    Keywords: Prejunctional α2-adrenoceptor ; Postjunctional α2-adrenoceptor ; α2-Adrenoceptor heterogeneity ; SK & F 104078
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Most α2-adrenoceptor antagonists do not discriminate between pre- and postjunctional α2-adrenoceptors, and this has led to the commonly held belief that pre- and postjunctional α2-adrenoceptors may represent one homogeneous population of receptors. SK&F 104078 has been shown to be a potent antagonist at postjunctional α2-adrenoceptors at concentrations that do not block prejunctional α2-adrenoceptors. Thus, SK & F 104078 is a competitive postjunctional α2-adrenoceptor antagonist in canine and rabbit saphenous veins, canine saphenous artery and human platelet with a dissociation constant of approximately 100 nmol/l. Conversely, SK & F 104078 is inactive as a prejunctional α2-adrenoceptor antagonist in atria from dog, guinea pig, rabbit and rat, and in guinea-pig ileum at concentrations up to 10,000 nmol/l. Likewise, SK & F 104078 has the ability to block postjunctional arterial α2-adrenoceptors in vivo in the pithed rat at doses that do not inhibit prejunctional α2-adrenoceptors in the same model. The results suggest that pre- and postjunctional α2-adrenoceptors may not represent one homogeneous class, but rather are discrete subtypes of the α2-adrenoceptor that may be differentiated by SK & F 104078.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stereoselectivity of carvedilol, a novel β-adrenoceptor antagonist and vasodilator with one asymmetric carbon atom, was examined at α1- and β1-adrenoceptors in vitro and in vivo. (-)-(S)-Carvedilol is a potent, competitive antagonist of the β1-adrenoceptor-mediated positive chronotropic response to isoproterenol in guinea pig atrium, with a dissociation constant (KB) of 0.4 nM. (+)-(R)-Carvedilol was more than 100-fold less potent than the (-)-S-enantiomer as an antagonist of β;1-andrenoceptors, having a KB of approximately 45 nM. Consistent with these findings (-)-(S)-carvedilol (0.1 mg/kg, i.v.) produced a 25-fold rightward shift in the β1-adrenoceptor-mediated positive chronotropic response to isoproterenol in pithed rats, whereas the (+)-R-enantiomer had no β1-adrenoceptor blocking activity in vivo at this dose. In contrast to the marked degree of stereoselectivity observed at βl1-adrenoceptors, both (-)-(S)- and (+)-(R)-carvedilol produced equal antagonism of the α1----adrenoceptor-mediated vasoconstrictor response to norepinephrine in rabbit aorta, with KB values of 14 and 16 nM, respectively. Furthermore, in the pithed rat, the α1-adrenoceptor-mediated pressor dose-response curve to cirazoline was shifted approximately 6-fold to the right by both the (+)-R- and (-)-S-enantiomers of carvedilol at a dose of 1 mg/kg, i.v. In anesthetized spontaneously hypertensive rats, (-)-(S)-carvedilol was 6-fold more potent as an antihypertensive than (+)-(R)-carvedilol. The vasodilator and acute antihypertensive activity of carvedilol results from α1-andrenoceptor blockade produced by both enantiomers, and the concomitant β1-adrenoceptor blockade produced by the (-)-S-enantiomer, which prevents reflex tachycardia that can offset the antihypertensive response, leading to greater overall antihypertensive potency of (-)-(S)-carvedilol relative to the (+)-R-enantiomer. These data also suggest that distinct regions of the carvedilol molecule are responsible for blocking α1- and β1-adrenoceptors, with β1-adrenoceptor blockade resulting from an area of the molecule containing the asymmetric carbon atom, specifically the carbazolyloxy propanolamine moiety, and α1-adrenoceptor blockade resulting from a part of the molecule that does not contain the asymmetric carbon atom, most likely the phenoxyethylamine moiety.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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