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THE EFFECTS OF CALCIUM ANTAGONISTS ON BLOOD PRESSURE AND RESPONSES TO α‐ADRENOCEPTOR AGONISTS IN HYPERTENSIVE RABBITS
Author(s) -
Hamilton C A.,
Jardine E.,
Sumner D. J.,
Reid J. L.
Publication year - 1987
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.1440-1681.1987.tb00960.x
Subject(s) - nifedipine , verapamil , phenylephrine , blood pressure , medicine , endocrinology , antagonist , calcium , heart rate , receptor
SUMMARY 1. The effects of the calcium antagonists verapamil and nifedipine on mean arterial blood pressure, heart rate and pressor responses to a range of α‐adrenoceptor agonists were examined in male normotensive New Zealand white rabbits and in rabbits with perinephritis hypertension. 2. Verapamil and nifedipine caused a greater fall in mean arterial pressure in hypertensive compared to normotensive rabbits both when the fall was expressed as an absolute and as a percentage change. Effects on heart rate were similar in normotensive and hypertensive animals. 3. Pressor responses to phenylephrine were attenuated by nifedipine and verapamil in normotensive and hypertensive rabbits. Pressor responses to alphamethyl noradrenaline were also attenuated by nifedipine, but pressor responses to BHT 920 were not significantly altered by either calcium antagonist in normotensive or hypertensive rabbits at the dose used. Thus the calcium antagonists had a greater effect on α 1 ‐than α 2 ‐adrenoceptor mediated responses in both normotensive and hypertensive rabbits. 4. Hypertensive animals showed an increased responsiveness to phenylephrine and alphamethyl noradrenaline but not BHT 920 compared to normotensives. This difference remained after treatment with both the calcium antagonists.