The differential effects of prazosin and hydralazine on sympathoadrenal activity in conscious rats

T. Kent Keeton, Ana M. Biediger

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)479-486
Number of pages8
JournalEuropean Journal of Pharmacology
Volume164
Issue number3
DOIs
StatePublished - May 30 1989
Externally publishedYes

Keywords

  • (Rat)
  • Hydralazine
  • Mean arterial pressure
  • Norepinephrine concentration (plasma)
  • Norepinephrine spillover rate
  • Prazosin

ASJC Scopus subject areas

  • Pharmacology

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