title: Silymarin potentiates the antinociceptive effect of morphine in mice.
abstract: Silymarin is a natural flavonoid found in the seeds of the milk thistle (Silybum marianum). Accumulating evidence indicates that silymarin exerts preventive/protective effects in animals and humans against many diseases. This study aimed to evaluate the antinociceptive effect of silymarin in the tail flick and writhing reaction assays. To understand the mechanism of the antinociceptive effect, the interaction of silymarin and morphine on acetic acid-induced reaction was examined. Moreover, the effect of naloxone as a narcotic receptor antagonist on silymarin-induced antinociception was studied. The antioxidant potency of silymarin was assessed by measuring the level of total thiol molecules in serum and the free radical scavenging activity. Silymarin lowered significantly (P < 0.05) the latency time in the tail flick test in a dose-dependent fashion. In the writhing reaction assay, silymarin dose- and time-dependently decreased the number of acetic acid-induced contractions. Silymarin also enhanced the morphine produced antinociceptive effect, while pretreatment with naloxone resulted in antagonism of the silymarin-induced antinociceptive effect, significantly (P < 0.05). Additionally, silymarin elevated the total thiol molecule level in the serum, which latter antioxidant property was confirmed by the concentration-dependent radical scavenging activity. The data suggest that the silymarin antinociceptive effect may be attributed to its interaction with the opioid system and its antioxidant capacity.
authors.affiliation: Department of Pharmacology and Toxicology, Faculty of Veterinary Medicine, Urmia University, P.O. Box 1177, Urmia, Iran. hassanmalekinejad@yahoo.com
authors.forename: Hassan
authors.initials: H
authors.lastname: Malekinejad
authors.forename: Maysam
authors.initials: M
authors.lastname: Taheri-Broujerdi
authors.forename: Masumeh
authors.initials: M
authors.lastname: Moradi
authors.forename: Seyed-Hamed
authors.initials: SH
authors.lastname: Tabatabaie
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D004357:Drug Synergism; D016166:Free Radical Scavengers / Q000494:pharmacology; D008297:Male; D051379:Mice; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology*; D012838:Silymarin / Q000494:pharmacology*; D013438:Sulfhydryl Compounds / Q000097:blood
chemical_list: D000701:Analgesics, Opioid; D016166:Free Radical Scavengers; D009292:Narcotic Antagonists; D012838:Silymarin; D013438:Sulfhydryl Compounds; D009270:Naloxone; D009020:Morphine