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Summary:Phyllantus amarus Schumach and Thonn is a medicinal plant used commonly for the treatment of malaria-related symptoms by the general public in southeastern Nigeria. The present study determines the possible antiplasmodial effects of the aqueous extract of the leaves and stem of the plant against Plasmodium berghei infection using Swiss albino mice as models. The blood schizonticidal activity of the aqueous extract in early infection and in established Plasmodium berghei infection was assessed and compared to the activities of chloroquine and sulfadoxine/pyrimethamine. The repository activity of the extract was also assessed and compared to the activity of pyrimethamine. The LD50 of the aqueous extract of the leaves and stem of the plant was also determined using albino Wistar rats. The results show that the LD50 of the aqueous extract of Phyllantus amarus Schumach and Thonn was 650 mg/kg. In early infection, the extract at doses of 108.33 mg/kg, 165 mg/kg and 325 mg/kg was found to cause a significant dose-dependent suppression of P berghei parasites (P<0.05) sulfadoxine/pyrimethamine caused a similar significant suppression of P berghei parasites (P<0.05) while chloroquine at a dose of 5 mg/kg did not cause a significant effect on P berghei parasites. Similarly, the extract was found at all doses to cause a statistically significant (P<0.05) suppression of P berghei parasites via a repository action. This effect was comparable to the effects of pyrimethamine a standard repository agent. In established infection, the extract at all doses administered, was found to significantly suppress P berghei parasites at 24 and 72-hour periods (P<0.05). Comparatively, sulfadoxine/pyrimethamine caused a similar statistical (P<0.05) suppression of the parasites of P berghei. However, the effects of sulfadoxine/pyrimethamine were more sustained over the 72-hour period. The present study therefore validates the local use of the extracts of Phyllantus amarus Schumach and Thonn as an antimalarial agent. Further studies are however recommended to identify and possibly characterize the potential antiplasmodial agents in the aqueous extract of the plant.

SUMMARY The investigation examines the hypothesis that metoclopramide-induced potentiation of gastrointestinal motility is mediated through dopamine receptors. In vitro studies on the longitudinal muscle of the guinea-pig ileum were performed. Metoclopramide, in concentrations comparable with those seen in plasma after therapeutic doses in man, selectively potentiated the cholinergic response. Metoclopramide can block dopamine, and its antiemetic effect probably involves antagonism of dopamine centrally.5 6 The presence of dopamine in gastrointestinal nerve7, raises the possibility tested here that metoclopramide acts peripherally by antagonising dopamine. MethodsExperiments were carried out on longitudinal muscle strips from guinea-pig ileum. Male guinea-pigs, 300-500g, were killed by a blow on the back of the head, bled out, and the terminal 30-40 cm ileum after discarding the last 20 cm was removed.Received for publication 22 June 1981 gastrointestinal motility does not involve local Longitudinal muscle strips 4-5 cm long, were prepared from the terminal ileum.8 Each strip was suspended under a load of 0.25 g in a 5 ml organ bath with built-in platinum electrodes. The bath contained Krebs-Henseleit solution: (mM) (NaCl, 113; KC1, 4.7; CaC12, 2.5; MgSO4, 1.2; KH2PO4, 1.2; NaHCO3, 25; glucose, 11.5), maintained at 37°C and bubbled with 95%0 2 and 5% CO2. Electrical stimulation was delivered from an electronic stimulator9, through the built-in platinum electrodes with a pulse duration of 0.2 ms, frequency 0 1 Hz and supramaximally effective voltage. Longitudinal muscle tone was monitored continuously using an isometric transducer and a pen-recorder. All experiments were performed a minimum of three times. DRUGSThe following drugs were dissolved in distilled water: acetylcholine chloride, atropine sulphate, dopamine hydrochloride, hexamethonium bromide, histamine chloride (Sigma); metoclopramide hydrochloride (Beecham Pharmaceuticals); phentolamine mesylate (Ciba); tetrodotoxin (Sigma).Bromocriptine methansulphonate (Sandoz) was dissolved in 30% ethyl alcohol to make 1.3 mM stock solution; further dilutions were made in Krebs solution. Pimozide (Janssen Pharmaceuticals) was dissolved in citric acid solution to make 5.5 mM stock solution and further diluted with distilled water. 66 on 10 May 2018 by guest. Protected by copyright.

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