Introduction: Active compounds derived from plants are able to inhibit nerve conduction. Cardamonin, a naturally occurring chalcone, manifests anti-nociceptive, anti-inflammatory and anti-neuropathy properties. Consequently, cardamonin may potentially inhibit nerve action potential, whereby, it affects the nerve conduction. Compound action potential is the sum of the activity which is measured from a nerve trunk. Objective: The experiment was carried out to investigate the inhibitory effect of cardamonin on compound action potentials and its possible mechanism of action on frog sciatic nerve. Methodology: LabTutor software was used to record compound action potentials in frog sciatic nerve. Sciatic nerve was isolated from the frog and soaked in Ringer’s solution. Stimulating electrodes were used to stimulate the nerve and recording electrodes were used to record compound action potentials. Compound action potential of the nerve were recorded before and after treatments [vehicle, cardamonin (0.5, 1 & 2 mg/ml) & morphine (3mg/ml)]. Participation of opioid system was investigated by pre-treating the nerve with naloxone and followed by cardamonin. All the data were recorded and analysed via LabTutor software. The data were analysed by using Two-way ANOVA followed by Bonferonni’s post hoc test with significant value at P < 0.05. Results: The outcomes showed that all the doses of cardamonin significantly reduced the peak amplitude of compound action potential in frog sciatic nerves. Besides, co-treatment of naloxone and cardamonin significantly (P < 0.001) reversed the effect of cardamonin on peak amplitude of compound action potential, suggesting the involvement of opioid receptors to inhibit nerve conduction. Conclusion: Cardamonin reduces the nerve signal conduction via activation of opioid receptors to modulate pain and contribute to the analgesic effects.
Neuropathic pain arises from the injury of nervous system. The condition is extremely difficult to be treated due to the ineffectiveness and presence of various adverse effects of the currently available drugs. In the present study, we investigated the antiallodynic and antihyperlagesic properties of cardamonin, a naturally occurring chalcone in chronic constriction injury (CCI)-induced neuropathic pain mice model. Our findings showed that single and repeated dose of intra-peritoneal administration of cardamonin (3, 10, 30mg/kg) significantly inhibited (P<0.001) the chronic constriction injury-induced neuropathic pain using the Hargreaves plantar test, Randall-Selitto analgesiometer test, dynamic plantar anesthesiometer test and the cold plate test in comparison with the positive control drug used (amitriptyline hydrochloride, 20mg/kg, i.p.). Pre-treatment with naloxone hydrochloride (1mg/kg, i.p.) and naloxone methiodide (1mg/kg, s.c) significantly reversed the antiallodynic and antihyperalgesic effects of cardamonin in dynamic plantar anesthesiometer test and Hargreaves plantar test, respectively. In conclusion, the current findings demonstrated novel antiallodynic and antihyperalgesic effects of cardamonin through the activation of the opioidergic system both peripherally and centrally and may prove to be a potent lead compound for the development of neuropathic pain drugs in the future.
Number of ligations made in the chronic constriction injury (CCI) neuropathic pain model has raised serious concerns. We compared behavioural responses, nerve morphology and expression of pain marker, c-fos among CCI models developed with one, two, three and four ligations. The numbers of ligation(s) on sciatic nerve shows no significant difference in displaying mechanical and cold allodynia, and mechanical and thermal hyperalgesia throughout 84 days. All groups underwent similar levels of nerve degeneration post-surgery. Similar c-fos level in brain cingulate cortex, parafascicular nuclei and amygdala were observed in all CCI models compared to sham-operated group. Therefore, number of ligations does not impact intensity of pain symptoms, pathogenesis and neuronal activation. A single ligation is sufficient to develop neuropathic pain, in contrast to the established model of four ligations. This study dissects and characterises the CCI model, ascertaining a more uniform animal model to surrogate actual neuropathic pain condition.