Fresh leaves from V. album plant was collected and extracted using standard methods. Acute toxicity studies showed that the crude extract had an LD 50 value of 417.5 mg/kg. mice, i.p. Based on this value, test doses (5-160mg/kg) below the LD 50 value were selected and used to determine the effects of each dose of extract on the arterial blood pressure (BP) and heart rate of normotensive and hypertensive rats. Some pharmacological agents like propranolol, noradrenaline, acetylcholine and atropine sulphate were also used to assess the mechanism of action of the extract on blood pressure. From the results, the extract produced a dose-dependent depression of blood pressure and heart rate in both normo-and hypertensive rats. At doses of 5mg/kg and 160mg/kg, the extracts produced about 8.99 + 3.2% and 54 + 7.4% depression of BP respectively, in normotensive rats while the corresponding values for the hypertensives were 4.8 + 2.3% and 43.9 + 5.5% respectively. The duration of action of the extract was also found to be dose-dependent. Noradrenaline (1.5 μg/kg) blocked the action of the extract. Both propranolol (1.0μg/kg) and atropine (1.5μg/kg) failed to block or abolish the action of the extract on rat BP. We suggest a non-adrenergic, non-cholinergic mechanism for the action of the extract on blood pressure.
Summary:The crude extract from E. drupifera leaves was prepared using standard methods. The rabbit intestine was removed and separated into three segments (duodenum, jejunum and ileum). About 3-4cm of each segment was mounted in an organ bath containing Tyrode solution at 37 + 1 o C. The spontaneous and rhythmic contractions were recorded and the effects of the crude extract (2-300μg/ml) on the tissue responses were investigated. The effect of Ca 2+ concentration and temperature of the bathing fluid were also studied. From the results, the extract (2-300g/ml) increased the amplitudes of contractions in a dose-dependent manner. However, regional differences occurred in the responsiveness of the tissue preparations. The ED 50 values were found to be 25.12, 44.67 and 15.85 μg/ml for the duodenum, jejunum and ileum respectively. Certain conditions such as calcium availability and increase in bath temperature favoured the action of the extract on the tissue preparations. Drugs like mepyramine or methysergide failed to influence the action of the extract. However, the extract-induced contractions were prevented or blocked by noradrenaline or atropine sulphate. The contractions were however ameliorated by the addition of acetyleholine or neostigmine to the bath solution.From the results, it is likely that the extract causes increased contractions of the tissue preparation via acetylcholine-like agent, which stimulates the muscarinic cholinoceptors.
Summary: Ninety male white Wistar rats (200 -320g) were fasted for 48 hours, and used in the experiments for the collection of gastric juice according to the method of Shay et al, 1954. The extract (2.5 -200 mg/kg) increased the secretion of gastric juice which was low in volume but rich in pepsin concentration.The adrenergic drugs dihydroergoergotoxine (hydergine) (1.25 mg/kg) and phentolamine (1.5 mg/kg) both also increased gastric secretion, which were high in volume, titratable acidity and total acid output but low in pepsin concentration. When the extract (20 mg/kg) was given in combination with either of the two sympatholytic drugs, the pepsin concentration in the juice was richer than that evoked by either of the two drugs alone. Also, atropine-extract combination significantly (P<0.01) increased gastric juice secretion when compared to that produced by atropine alone. Similar increase in acid secretion was observed when cimetidine-extract combination was administered and compared to that produced by cimetidine alone. We suggest a dual pathway mechanism of action for the E. drupifera leaf extract-induced secretion of gastric juice. One of which may be mediated by the muscarinic cholinoceptors and the other via histamine H 2 -receptor subtype.
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