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The pharmacological effects of Ratree (Cestrum nocturnum Linn.) leaves extracts were studied in both rat sciatic nerve-gastrocnemius preparations in situ and isolated rat phrenic nerve-hemidiaphragm preparations. The extracts produced twitch potentiation followed by depressive effect on neuromuscular transmission. All doses of the extracts (0.33-0.267 mg/kg body weight) initially produced a slight twitch potentiation which was followed by neuromuscular blockade in the in situ study. In the isolated rat phrenic nerve-hemidiaphragm preparation, the alcoholic extract in the dose of 0.36 mg/ml produced only the increase in twitch amplitude; higher doses (1.43-11.42 mg/ml) decreased the muscle contraction. The alcoholic extract significantly increased the neuromuscular blocking effect of pancuronium and succinylcholine. The neuromuscular depression produced by this extract was not antagonized by physostigmine, tetraethylammonium and Ca2+. The neurogenic post-tetanic potentiation (PTP) was partially blocked by this extract as well as by succinylcholine. Besides these effects, the extract caused muscle contraction with slightly increased in amplitude and prolonged duration; subsequently,it also produced spontaneous muscle contraction (fasciculation). This muscle fasciculation and contraction were abolished by pancuronium. LD50 of the extract, when given i.p. to rats, was found to be 2.65 g/kg body weight. The active constituent may be saponins and certain alkaloids. The muscle relaxant property of the extract was probably due to saponins, since the decreased in twitch amplitude produced by the extract was similar to that of standard saponins. Besides neuromuscular effects, the extracts from this plant produced hypotension and decreased in intestinal tension in rats.
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