TY - JOUR
T1 - The differential effects of prazosin and hydralazine on sympathoadrenal activity in conscious rats
AU - Kent Keeton, T.
AU - Biediger, Ana M.
N1 - Funding Information:
The prazosin and hydralazine used in these studies were gifts from Pfizer Central Research of Pfizer, Inc., and the Ciba Pharmaceutical Division of Ciba-Geigy Corporation, respectively. These studies were supported by a grant from the National Institutes of Health (HL 36080).
PY - 1989/5/30
Y1 - 1989/5/30
N2 - The ability of the vasodilator hydralazine and the α1-adrenoceptor antagonist prazosin to increase sympathoadrenal outflow was compared by measuring plasma norepinephrine and epinephrine and epinephrine concentrations, norepinephrine clearance and norepinephrine spillover rate into plasma in conscious Sprague-Dawley rats and spontaneously hypertensive rats (SHR). Even though vasodepressor effect of 1 mg/kg (i.p.) of prazosin (-23 mm Hg) was significantly less than that caused by 1 mg/kg (i.p.) of hydralazine (-31 mm Hg) in normotensive rats, the increases in plasma norepinephrine concentration and norepinephrine spillover rate were significantly larger in prazosin-treated rats. In conscious SHR, 0.5 mg/kg (i.p.) of prazosin and 0.3 mg/kg (i.p.) of hydralazine lowered blood pressure to the same extent (-22 mm Hg), but prazosin again produced significantly larger increases in plasma norepinephrine concentration and norepinephrine spillover rate. Neither prazosin nor hydralazine affected norepinephrine clearance, and only prazosin elicited a significant rise in plasma epinephrine concentration. This differential effect of prazosin and hydralazine on sympathoadrenal activity is best explained by the differing effects of these drugs on veneous return and thus the afferent activity of the cardiopulmonary baroreceptors.
AB - The ability of the vasodilator hydralazine and the α1-adrenoceptor antagonist prazosin to increase sympathoadrenal outflow was compared by measuring plasma norepinephrine and epinephrine and epinephrine concentrations, norepinephrine clearance and norepinephrine spillover rate into plasma in conscious Sprague-Dawley rats and spontaneously hypertensive rats (SHR). Even though vasodepressor effect of 1 mg/kg (i.p.) of prazosin (-23 mm Hg) was significantly less than that caused by 1 mg/kg (i.p.) of hydralazine (-31 mm Hg) in normotensive rats, the increases in plasma norepinephrine concentration and norepinephrine spillover rate were significantly larger in prazosin-treated rats. In conscious SHR, 0.5 mg/kg (i.p.) of prazosin and 0.3 mg/kg (i.p.) of hydralazine lowered blood pressure to the same extent (-22 mm Hg), but prazosin again produced significantly larger increases in plasma norepinephrine concentration and norepinephrine spillover rate. Neither prazosin nor hydralazine affected norepinephrine clearance, and only prazosin elicited a significant rise in plasma epinephrine concentration. This differential effect of prazosin and hydralazine on sympathoadrenal activity is best explained by the differing effects of these drugs on veneous return and thus the afferent activity of the cardiopulmonary baroreceptors.
KW - (Rat)
KW - Hydralazine
KW - Mean arterial pressure
KW - Norepinephrine concentration (plasma)
KW - Norepinephrine spillover rate
KW - Prazosin
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U2 - 10.1016/0014-2999(89)90255-0
DO - 10.1016/0014-2999(89)90255-0
M3 - Article
C2 - 2767118
AN - SCOPUS:0024335977
VL - 164
SP - 479
EP - 486
JO - European Journal of Pharmacology
JF - European Journal of Pharmacology
SN - 0014-2999
IS - 3
ER -