ISSN:
1440-1681
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
1. The intrinsic sympathomimetic acitivity of a range of β-adrenoceptor antagonists and its relationship to β-adrenoceptor blockade was studied in pentobarbitone-anaesthetized, vagotomized rats which had been depleted of catecholamines by pretreatment with syrosingopine.Dichlorisoprenaline, practolol, oxprenolol, pindolol and acebutolol, produced dose-dependent positive chronotropic responses in this preparation.2. The relationship between the dose requirements for this intrinsic sympathomimetic activity and β-adrenoceptor-blocking activity was not the same for all drugs: (i) dichlorisoprenaline and practolol had intrinsic activity at all β-adrenoceptor-blocking doses; and (ii) oxprenolol, pindolol and acebutolol had predominantly β-adrenoceptor blockade at the lower dose levels and agonist activity only became significant at high doses relative to those producing β-adrenoceptor blockade.3. The positive chronotropic response to both practolol and pindolol was observed in rats which had been pithed and was antagonized by propranolol (0.1-3.0 mg/kg, i.v.), indicating that β-adrenoceptors were involved.4. It was concluded that the intrinsic sympathomimetic activity of β-adrenoceptor antagonists was not a simple property as it was described by the relationship between the dose requirements for intrinsic sympathomimetic activity and for β-adrenoceptor blockade as well as the degree of partial agonist activity.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1440-1681.1979.tb00001.x
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