title: Effects of the aqueous extract of Pittosporum mannii Hook. f. (Pittosporaceae) stem barks on spontaneous and spasmogen-induced contractile activity of isolated rat duodenum.
abstract: BACKGROUND
  Pittosporum mannii Hook. f. (Pittosporaceae) is a plant widely used in traditional medicine in Cameroon for the treatment of many gastrointestinal disorders including diarrhea. To date, no pharmacological study on the antidiarrheal and the antispasmodic properties of this plant has been reported. The aim of the present study was to evaluate in vitro the relaxant activity of the aqueous extract of stem barks of P. mannii (PMAE) on rat duodenum.
  
  
  METHODS
  Different concentrations of PMAE were tested separately (10-80 µg/mL) or cumulatively (5-80 µg/mL) on spontaneous and spasmogen (carbachol, histamine and KCl)-induced contractions of isolated rat duodenum strips.
  
  
  RESULTS
  At concentrations ranging from 10 to 80 µg/mL, PMAE significantly decreased the tonus and the amplitude of spontaneous contractions. However, at high concentration (80 µg/mL), the extract elicited a transient relaxation was followed by a slight increase of tonus, while the amplitude remained lower compared to the normal spontaneous activity. The relaxant effect of the extract was not significantly affected in the presence of atropine (0.713 µg/mL) and promethazine (0.5 µg/mL). In addition, PMAE (20, 40, and 80 µg/mL) partially but significantly inhibited in a concentration related manner the contractions induced by carbachol (10(-9)-10(-4)M) and histamine (10(-9)-10(-4)M) on rat duodenum. PMAE (10-80 µg/mL) also significantly induced a concentration-dependent relaxation on KCl (20mM, 50mM, 10(-3)-6.10(-3)M)-induced contraction of rat duodenum.
  
  
  CONCLUSIONS
  These results show that the aqueous extract of P. mannii stem barks possesses antispasmodic and spasmolytic effects at lower concentrations; therefore, supporting the use of the stem barks of this plant in the folk medicine for the treatment of diarrhea. However, caution should be paid while using higher concentrations that instead might produce spasmogenic effect and might worsen the diarrheal condition. The relaxant effect of PMAE appears to be non-specific of muscarinic or histaminic receptors, but may involve at least in part a mechanism of inhibition of the Ca(2+) influx into the smooth muscle cells through voltage-operated Ca(2+) channels.
authors.affiliation: Laboratory of Animal Physiology, Department of Animal Biology, Faculty of Science, University of Yaounde I, PO Box 812, Yaounde, Cameroon.
authors.forename: Njiaza
authors.initials: N
authors.lastname: Joseph
authors.affiliation: Laboratory of Animal Physiology, Department of Biological Sciences, High Teachers׳ Training College, University of Yaounde I, PO Box 47, Yaounde, Cameroon.
authors.forename: Ngo Lemba
authors.initials: NL
authors.lastname: Tom Esther
authors.affiliation: Laboratory of Animal Physiology and Phytopharmacology, Department of Animal Biology, Faculty of Science, University of Dschang, PO Box 67, Dschang, Cameroon.
authors.forename: Nguelefack
authors.initials: N
authors.lastname: Télesphore Benoît
authors.affiliation: Laboratory of Animal Physiology, Department of Animal Biology, Faculty of Science, University of Yaounde I, PO Box 812, Yaounde, Cameroon.
authors.forename: Dzeufiet Djomeni
authors.initials: DD
authors.lastname: Paul Désiré
authors.affiliation: Laboratory of Animal Physiology, Department of Animal Biology, Faculty of Science, University of Yaounde I, PO Box 812, Yaounde, Cameroon.
authors.forename: Aboubakar
authors.initials: A
authors.lastname: Oumarou Bibi-Farouck
authors.affiliation: Laboratory of Animal Physiology, Department of Animal Biology, Faculty of Science, University of Yaounde I, PO Box 812, Yaounde, Cameroon. Electronic address: dimo59@yahoo.com.
authors.forename: Dimo
authors.initials: D
authors.lastname: Théophile
authors.affiliation: Laboratory of Animal Physiology, Department of Animal Biology, Faculty of Science, University of Yaounde I, PO Box 812, Yaounde, Cameroon.
authors.forename: Kamtchouing
authors.initials: K
authors.lastname: Pierre
mesh_terms: D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002217:Carbachol / Q000037:antagonists & inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004386:Duodenum / Q000187:drug effects* / Q000502:physiology; D006632:Histamine / Q000494:pharmacology; D006633:Histamine Antagonists / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008519:Medicine, Traditional; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D010276:Parasympatholytics / Q000494:pharmacology; D024301:Plant Bark / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology*; D018547:Plant Stems / Q000737:chemistry*; D011189:Potassium Chloride / Q000037:antagonists & inhibitors / Q000494:pharmacology; D011398:Promethazine / Q000494:pharmacology; D051381:Rats; D019685:Rosales / Q000737:chemistry*
chemical_list: D006633:Histamine Antagonists; D010276:Parasympatholytics; D010936:Plant Extracts; D011189:Potassium Chloride; D001285:Atropine; D006632:Histamine; D002217:Carbachol; D011398:Promethazine
keywords: Pittosporum mannii; Rat duodenum; Relaxant effect; Spasmogen-induced contractions; Spontaneous contractions