Authors : Z.A. Zakaria , M.N. Somchit , M.R. Sulaiman , A.M. Mat Jais and C.A. Fatimah
Abstract: The present study was carried out to determine the involvement of various receptor antagonists in and the effect of pH and enzymes on the recently reported antinociceptive activity of aqueous extract of Muntingia calabura leaves (MCAE) using the abdominal constriction test. The extract was prepared by soaking the dried powdered leaves of M. calabura in distilled water (dH2O) overnight and the supernatant obtained was considered as a stock solution with 100% concentration/strength. The MCAE, administered s.c. at the concentrations of 5, 50 and 100%, were found to show significant antinociceptive activity in a concentration-dependent manner. The 50% concentration MCAE was further used to study on the above mentioned parameters. The extract exhibited significant (p<0.05) decreased in activity when pre-treated (s.c.) against 10 mg kg-1 naloxonazine, 10 mg kg-1 pindolol and 5 mg kg-1 atropine, but not 10 mg kg-1 -funaltreaxamine, 10 mg kg-1 naltrindole, 10 mg kg-1 phenoxybenzamine, 10 mg kg-1 bicuculine or 5 mg kg-1 mecamylamine, respectively. The extract exhibited significant (p<0.05) increased in activity after pre-treatment at alkaline pH (pH 9 and 11) while maintaining the activity at the extreme acidic and alkaline conditions (pH 2 and pH 13), respectively. The extract activity was not changed after pre-treatment against -amylase, protease, lipase or their combination, when compared to the dH2O-pre-treated group, respectively. Based on the results, we conclude that the M. calabura leaves peripheral antinociception involved, at least in part, activation of �-opioid, -adrenergic and muscarinic receptors and resist the effect of extreme acidic and alkaline conditions as well as various enzymes.
Z.A. Zakaria , M.N. Somchit , M.R. Sulaiman , A.M. Mat Jais and C.A. Fatimah , 2008. Effects of Various Receptor Antagonists, pH and Enzymes on Muntingia calabura Antinociception in Mice. Research Journal of Pharmacology, 2: 31-37.