Assessment of antinociceptive property of Cynara scolymus L. and possible mechanism of action in the formalin and writhing models of nociception in mice

Abstract

Background: Cynara scolymus has bioactive constituents and has been used for therapeutic actions. The present study was undertaken to investigate the mechanisms underlying pain-relieving effects of the hydroethanolic extract of C. scolymus (HECS).

Methods: The antinociceptive activity of HECS was assessed through formalin and acetic acid-induced writhing tests at doses of 50, 100 and 200 mg/kg intraperitoneally. Additionally, naloxone (non-selective opioid receptors antagonist, 2 mg/kg), atropine (non-selective muscarinic receptors antagonist, 1 mg/kg), chlorpheniramine (histamine HH₁-receptor antagonist, 20 mg/kg), cimetidine (histamine H₂-receptor antagonist, 12.5 mg/kg), flumazenil (GABA_A/BDZ receptor antagonist, 5 mg/kg) and cyproheptadine (serotonin receptor antagonist, 4 mg/kg) were used to determine the systis implicated in HECS-induced analgesia. Impact of HECS on locomotor activity was executed by open-field test. Determination of total phenolic content (TPC) and total flavonoid content (TFC) was done. Evaluation of antioxidant activity was conducted iploying 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay.

Results: HECS (50, 100 and 200 mg/kg) significantly indicated dose dependent antinociceptive activity against pain-related behavior induced by formalin and acetic acid (P < 0.001). Pretreatment with naloxone, atropine and flumazenil significantly reversed HECS-induced analgesia. Antinociceptive effect of HECS riained unaffected by chlorpheniramine, cimetidine and cyproheptadine. Locomotor activity was not affected by HECS. TPC and TFC of HECS were 59.49 ± 5.57 mgGAE/g dry extract and 93.39 ± 17.16 mgRE/g dry extract, respectively. DPPH free radical scavenging activity (IC₅₀) of HECS was 161.32 ± 0.03 μg/mL.

Conclusions: HECS possesses antinociceptive activity which is mediated via opioidergic, cholinergic and GABAergic pathways.

Keywords: Analgesic; Cholinergic Agents; Cynara scolymus; GABA; Mice; Opioid; Pain Measurient.

Fig. 1

Effect of HECS (50, 100 and 200 mg/kg) and morphine (5 mg/kg) on the formalin-induced pain responses (A). Effect of pretreatment with naloxone (non-selective opioid receptors antagonist, 2 mg/kg) (B), atropine (non-selective muscarinic receptor antagonist, 1 mg/kg) (C), chlorpheniramine (histamine H1-receptor antagonist, 20 mg/kg) (D), cimetidine (histamine H2-receptor antagonist, 12.5 mg/kg) (E), flumazenil (GABAA/BDZ receptor antagonist, 5 mg/kg) (F) and cyproheptadine (serotonin receptor antagonist, 4 mg/kg) (G) on the antinociceptive activity of HECS in formalin-induced pain responses. Data are expressed as mean ± standard error of mean (n = 6 mice in each group). Data were analyzed using one-way ANOVA followed by Tukey’s HSD post-hoc test. HECS: hydroethanolic extract of Cynara scolymus. *P < 0.05: compared with control group in each phase. #P < 0.05: compared with HECS (200 mg/kg)-treated group in each phase.

Fig. 2

Effect of HECS (50, 100 and 200 mg/kg) and indomethacin (5 mg/kg) on the acetic acid-induced writhing (A). Effect of pretreatment with naloxone (non-selective opioid receptors antagonist, 2 mg/kg) (B), atropine (non-selective muscarinic receptor antagonist, 1 mg/kg) (C), chlorpheniramine (histamine H1-receptor antagonist, 20 mg/kg) (D), cimetidine (histamine H2-receptor antagonist, 12.5 mg/kg) (E), flumazenil (GABAA/BDZ receptor antagonist, 5 mg/kg) (F) and cyproheptadine (serotonin receptor antagonist, 4 mg/kg) (G) on the antinociceptive activity of HECS in acetic acid-induced writhing. Data are expressed as mean ± standard error of mean (n = 6 mice in each group). Data were analyzed using one-way ANOVA followed by Tukey’s HSD post-hoc test. HECS: hydroethanolic extract of Cynara scolymus. *P < 0.05: compared with control group. #P < 0.05: compared with HECS (200 mg/kg)-treated group.

Fig. 3

Effect of treatment of mice with HECS (50, 100 and 200 mg/kg) on the number of crossings (A) and number of rearings (B) in the open-field test. Data are expressed as mean ± standard error of mean (n = 6 mice in each group). HECS: hydroethanolic extract of Cynara scolymus, i.p.: intraperitoneal.