Assessing novel antinociceptive mechanisms and anxiolytic effects of a combination of orphenadrine and diclofenac in experimental mice: In silico, molecular and histological perspectives.

Résumé

Background: Orphenadrine is a muscle relaxant while diclofenac is a non-steroidal anti-inflammatory agent. This study examined whether orphenadrine and diclofenac possess any synergistic antinociceptive and antianxiety effect, and the possible mechanisms involved.

Methods: Mice were allotted into four groups, containing six animals. Group I, distilled water (10 mL/kg, po), groups II, III and IV received diclofenac (50 mg/kg ip), orphenadrine (20 mg/kg, po), orphenadrine (20 mg/kg) + diclofenac (50 mg/kg), respectively. Thirty minutes after (1 hour for groups I and III), mice were injected with 0.6 % acetic acid (10 ml/kg, ip), and the number of stretches were recorded for 30 minutes. Twenty-four hours after, all groups were subjected to the hole-board assay. The mice were euthanized, and their brains were isolated for biochemical, histological, and semi-quantitative RT-PCR assays.

Results: Orphenadrine and diclofenac reduced the number of stretches, while their combination exerted a significant 90 ±0.5 % reduction (p<0.01). Only the combination significantly increased the head dips relative to all treatment groups (p<0.05). Tumour necrosis factor (TNF)-? level was increased in the combination group compared to all groups (p<0.05).  Cyclooxygenase (COX) expression was reduced in the orphenadrine and combination groups compared with the control (p<0.01). Histology revealed distortions in the kidney and brain of all treated groups. In Silico studies showed that orphenadrine had moderate binding affinity for serotonin (5HT₂), and COX.

Conclusions: The data indicates that the orphenadrine + diclofenac combination exerts synergistic antinociceptive and antianxiety effects that may involve activation of serotonin receptors, and inhibition of COX expression.