Biomolecules & Therapeutics

The Korean Society of Applied Pharmacology (한국응용약물학회)
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Cholinomimetic Properties of a Water-Soluble Fraction from Mulberry Leaves in Rats

  • Lee, Ju-Seon (Drug and Toxicology Division, National Institute of Scientific Investigation) ;
  • Chung, Sung-Hyun (College of Pharmacy, Kyung Hee University) ;
  • Lee, Yong-Sup (College of Pharmacy, Kyung Hee University) ;
  • Jin, Chang-Bae (Bioanalysis and Biotransformation Research Center, Korea Institute of Science and Technology)
  • Published : 2005.03.01
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Abstract

The present study examined effects of a water-soluble fraction from mulberry leaves (ML water fraction) on the circulatory and autonomic nervous systems, which were compared with those of acetylcholine (ACh) used as a reference drug in order to elucidate its mechanism of action. Intravenous administration of ACh or a ML water fraction produced temporary depressor and tachycardiac responses in a dose-dependent manner in unrestrained, conscious Sprague-Dawley rats. The systemic hemodynamic effects of ACh and a ML water fraction were almost completely blocked by pretreatment with atropine, a muscarinic antagonist. The depressor responses to ACh and a ML water fraction were slightly enhanced and prolonged by pretreatment with neostigmine, an anticholinesterase, whereas the tachycardiac responses were remarkably blocked by pretreatment with pentolinium, a ganglionic blocking agent. In vitro experiments using the ileum isolated from rats showed that ACh and a ML water fraction increased ileal contractility in a dose-dependent manner. The increases in ileal contractility were also completely abolished in the presence of atropine. Finally, the specific binding of [$^3H$]quinuclidinyl benzilate, a muscarinic antagonist, to rat cortical synaptic membranes was inhibited by a ML water fraction in a concentration-dependent manner with an IC$_{50}$ value of 9.5 mg/ml. The results suggest that the effects of a ML water fraction are mediated through direct stimulation of muscarinic cholinergic receptors by unknown cholinomimetic substance(s) contained in that fraction.

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References

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