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DISEASE‐INDUCED CHANGES IN α‐ADRENOCEPTOR‐MEDIATED CARDIAC AND VASCULAR RESPONSES IN RATS
Author(s) -
Brown Lindsay,
Amos Gregory,
Miller Brendan
Publication year - 1994
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1994.tb02575.x
Subject(s) - phenylephrine , inotrope , medicine , endocrinology , agonist , adrenergic , receptor , blood pressure
SUMMARY 1. The physiological relevance of cardiac and vascular α‐adrenoceptors may increase in disease states in which β‐adrenoceptors are altered. To test this, positive inotropic and vasoconstrictor responses to phenylephrine were measured in isolated tissues from rats with experimentally‐induced hyperthyroidism, hypothyroidism and diabetes as well as in genetically spontaneous hypertensive rats (SHR). 2. In left atria, positive inotropic responses to phenylephrine were increased in hypothyroid and diabetic rats and abolished in hyperthyroid and SHR. 3. In contrast, phenylephrine produced increased positive inotropy in left ventricular papillary muscles from hyperthyroid rats, increased potency in diabetic rats and negative inotropic responses in hypothyroid rats. 4. The potency of phenylephrine as a vasoconstrictor in thoracic aortic rings was increased in hyperthyroid and SHR and decreased in hypothyroid rats. 5. Thus, disease states which alter β‐adrenoceptor responsiveness can independently regulate atrial, ventricular and vascular responses to the α 1 ‐adrenoceptor agonist, phenylephrine. Therefore, these disease states may alter the physiological control of the cardiovascular system by noradrenaline and adrenaline as well as the responsiveness in disease states to therapeutic agents acting via α‐adrenoceptors.