Naloxone-induced reversal of clonidine, but not hydralazine, hypotension

✍ Scribed by Debra A. Bennett; John J. DeFeo; Edward E. Elko; Harbans Lal

• Book ID: 102146459
• Publisher: John Wiley and Sons
• Year: 1982
• Tongue: English
• Weight: 302 KB
• Volume: 2
• Category: Article
• ISSN: 0272-4391
• DOI: 10.1002/ddr.430020207

✦ Synopsis

Abstract

Normotensive rats of the Sprague‐Dawley strain were administered either the centrally acting hypotensive drug clonidine (0.16 mg/kg IP) or the peripherally acting hypotensive drug hydralazine (1.25 mg/kg IP) to induce reliable hypotension (blood pressure reductions of 60–90 mm Hg), as measured by a tail cuff procedure. The opiate antagonist, naloxone (10–20 mg/kg IP), reversed clonidine but not hydralazine hypotension. Naloxone also failed to reverse hydralazine's hypotensive action in rats made hypertensive by renal ligation. Naloxone's reversal of clonidine (0.01 mg/kg IV) hypotension was confirmed in experiments in which blood pressure was measured through direct cannulation of the carotid artery. It is suggested that naloxone's antagonism of clonidine hypotension is located at a central nervous system site, and that clonidine hypotension may be mediated through an interaction with the brain opiate systems.