Harungana madagascariensis (Hypericaceae) is used in the center region of Cameroon for hypertension by traditional healers. Also no scientific works has been undertaken on this pharmacology aspect, the present study was aimed to assess the effects of an aqueous extract of Harungana madagascariensis (AEHM) on arterial blood pressure and the involved mechanisms in urethane anaesthetized Wistar rats. Their blood pressure was measured from the left common carotid artery connected to a pressure transducer. The AEHM (5, 10, 15 and 20 mg/kg) was administered via the right femoral vein in a pilot study in 4 groups of 5 animals each. H. madagascariensis produced a dose-related hypotension. The dose 20 mg/kg which produced the highest immediate hypotension and bradycardia from the 45th min to the end of the recording period (60th min) was selected for the mechanisms studies. The hypotension produced by 20 mg/kg dose of the extract was significantly (P<0.05) inhibited by atropine and yohimbine but not by propranolol, indomethacin or cimetidine. This indicates that H2-histaminergic, β2-adrenergic and cyclooxygenase pathways are not likely to be involved in the hypotension produced by the extract, however, its might contain active compounds possessing cholinergic-receptor agonist action and acting through a reduction of sympathetic outflow and reduction of synaptic norepinephrine. These results may explain the use of this plant by traditional healers to treat hypertension.
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2022: 6.012
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