NALOXONE REVERSES THE ANTIHYPERTENSIVE EFFECT OF CLONIDINE

CSABA FARSANG, GEORGE KUNOS

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Abstract

In unanaesthetized, spontaneously hypertensive rats the decrease in blood pressure and heart rate produced by intravenous clonidine, 5 to 20 μg/kg, was inhibited or reversed by naloxone, 0.2 to 2 mg/kg. The hypotensive effect of 100 mg/kg α‐methyldopa was also partially reversed by naloxone. Naloxone alone did not affect either blood pressure or heart rate. In brain membranes from spontaneously hypertensive rats clonidine, 10−8 to 10−5 m, did not influence stereoselective binding of [3H]‐naloxone (8 nm), and naloxone, 10−8 to 10−4 m, did not influence clonidine‐suppressible binding of [3H]‐dihydroergocryptine (1 nm). These findings indicate that in spontaneously hypertensive rats the effects of central α‐adrenoceptor stimulation involve activation of opiate receptors. As naloxone and clonidine do not appear to interact with the same receptor site, the observed functional antagonism suggests the release of an endogenous opiate by clonidine or α‐methyldopa and the possible role of the opiate in the central control of sympathetic tone. 1979 British Pharmacological Society

Original languageEnglish
Pages (from-to)161-164
Number of pages4
JournalBritish journal of pharmacology
Volume67
Issue number2
DOIs
Publication statusPublished - Oct 1979

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ASJC Scopus subject areas

  • Pharmacology

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