Open AccessRole of the α-Adrenergic Blocking Effect in the Acute Hypotensive Effect of β-Adrenergic Blocking Drugs with α-Blocking Activities in Conscious SHR
Author(s) -
Hiroyuki Nakahara,
Makoto Nakazawa,
Kazuki Takeda,
Shoichi Imai
Publication year - 1985
Publication title -
japanese journal of pharmacology/japanese journal of pharmacology
Language(s) - English
Resource type - Journals
eISSN - 1347-3506
pISSN - 0021-5198
DOI - 10.1254/jjp.39.487
Subject(s) - prazosin , propranolol , phenylephrine , labetalol , blocking (statistics) , blood pressure , adrenergic receptor , hydralazine , pharmacology , medicine , adrenergic , alpha (finance) , adrenergic antagonist , endocrinology , antagonist , receptor , surgery , construct validity , statistics , mathematics , patient satisfaction
Acute hypotensive effects and the mechanisms of three beta-adrenergic blocking drugs with alpha-blocking activity were studied in comparison with those of prazosin, propranolol and hydralazine in the conscious spontaneously hypertensive rat (SHR). Prazosin lowered the blood pressure dose-dependently and inhibited the pressor response to phenylephrine. Three beta-adrenergic blocking drugs with alpha-blocking activity, labetalol (30 mg/kg), arotinolol (100 mg/kg) and nipradilol (100 mg/kg) also lowered the blood pressure to the same extent as prazosin (0.3 mg/kg), but the inhibition of the pressor response to phenylephrine produced by them was disproportionately slight. Propranolol (100 mg/kg) did not lower the blood pressure. These results suggest that the acute hypotensive effects of three beta-adrenergic blocking drugs with alpha-blocking activity were attributable only partially to the alpha-adrenergic blocking effect; a mechanism or mechanisms other than the alpha-adrenergic blocking effect must be invoked to explain the acute hypotensive effect produced by lower doses of these drugs in the conscious SHR.