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INVOLVEMENT OF THE ADRENAL GLANDS IN THE HYPOTENSIVE RESPONSE TO BROMOCRIPTINE IN SPONTANEOUSLY HYPERTENSIVE RATS
Author(s) -
HAMILTON T.C.
Publication year - 1981
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.1476-5381.1981.tb10992.x
Subject(s) - bromocriptine , endocrinology , propranolol , medicine , haloperidol , methysergide , atenolol , dopamine agonist , sulpiride , agonist , pimozide , blood pressure , phenoxybenzamine , metoclopramide , pharmacology , dopamine , antagonist , prolactin , hormone , dopaminergic , receptor , vomiting
1 The dopamine agonist, bromocriptine, produced a hypotensive response following oral administration to conscious normotensive and spontaneously hypertensive (SH‐) rats. 2 In SH‐rats the dose‐related falls in blood pressure to bromocriptine, 3 to 30 mg/kg orally or intraperitoneally, were biphasic, an initial fall at 1 h being followed by some recovery at 2 h and a subsequent fall in blood pressure at 4 and 6 h. 3 The dopamine antagonists, metoclopramide, sulpiride, haloperidol and pimozide, had little or no effect on the hypotensive response to bromocriptine, 10 mg/kg orally, in SH‐rats. 4 Pretreatment with α‐methyl‐ p ‐tyrosine augmented the hypotensive response to bromocriptine, 10 mg/kg orally, in SH‐rats. 5 In adrenal demedullated SH‐rats, the hypotensive response to bromocriptine, 3 to 30 mg/kg orally, was abolished. 6 In SH‐rats the hypotensive response to bromocriptine, 10 mg/kg orally, was prevented by the β‐adrenoceptor blocking drugs, propranolol and oxprenolol, but was unaffected by (+)‐propranolol and by the cardio‐selective β‐adrenoceptor blocking drug, atenolol. 7 In SH‐rats pretreated with bromocriptine, 10 mg/kg orally, and then anaesthetized, the pressor responses to low doses of intravenous adrenaline were reversed to depressor, indicating that bromocriptine possesses α‐adrenoceptor blocking activity. 8 The results suggest that the hypotensive response to bromocriptine in conscious SH‐rats is mediated by adrenaline released from the adrenal medullae which, in the presence of α‐adrenoceptor blockade, stimulates vascular β‐adrenoceptors producing vasodilatation.