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An analysis of the coronary vascular responses to catecholamines, using a modified Langendorff heart preparation
Author(s) -
BROADLEY K. J.
Publication year - 1970
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1970.tb10642.x
Subject(s) - chronotropic , dilator , medicine , inotrope , vasodilation , vasoconstriction , isoprenaline , heart rate , coronary perfusion pressure , constriction , cardiology , perfusion , stimulation , endocrinology , blood pressure , anesthesia , cardiopulmonary resuscitation , resuscitation
Summary1 . A modified Langendorff heart preparation from the guinea‐pig was used to analyse catecholamine responses. Contractile force, heart rate and coronary perfusion pressure were recorded. 2 . Four components of the vascular response could be identified.(a) The initial phase was a vasoconstriction mediated by α‐adrenoceptors which preceded any effects on heart rate and force. (b) A secondary constriction followed, which was due to the increased myocardial compression during positive inotropic and chronotropic responses. (c) The third, more predominant, effect was a prolonged dilatation probably associated with the increased metabolic activity of the heart. (d) A fourth component was a direct vasodilatation mediated by β‐adrenoceptors which was evident when small doses of catecholamines were used but was usually masked by the more pronounced metabolically linked dilatation.3 . The actions of salbutamol were examined and since it caused direct vasodilatation by stimulation of β‐adrenoceptors without other myocardial effects, these adrenoceptors were classified as the β 2 ‐type. 4 . I.C.I. 50,172 was employed to block selectively the myocardial effects due to stimulation of β 1 ‐adrenoceptors and leave the vasodilator β 2 ‐adrenoceptors unaffected. 5 . Adrenaline, noradrenaline and isoprenaline were compared at two dose levels, in the presence or absence of effects on heart rate and force. 6 . Constrictor or dilator effects were found in the absence of other effects and were shown to depend to some extent on the rate of coronary perfusion.