Examination of the antiallodynic effect of rosmarinic acid in neuropathic pain and possible mechanisms of action.

This study aimed to explore the potential antiallodynic effects of rosmarinic acid, a natural antioxidant with a demonstrated safety profile across a broad dose range. Using a chronic constriction injury-induced neuropathic pain model, the impact of rosmarinic acid on allodynia was investigated. Furthermore, the involvement of adrenergic and opioidergic mechanisms in its activity was assessed. To evaluate rosmarinic acid's efficacy, doses of 10, 20, and 40 mg/kg were administered and the electronic von Frey test was utilized along with an activity cage apparatus. % MPE values were calculated to gauge the extent of pain relief. Mechanistic insights were obtained by pretreating animals with the β-adrenergic receptor antagonist propranolol, the α1-adrenergic receptor antagonist prazosin, α2-adrenergic receptor antagonist yohimbine, and the opioid receptor antagonist naloxone. Rosmarinic acid demonstrated a statistically significant antiallodynic effect that was independent of locomotor activity. This effect was noteworthy as it resembled both the level and duration of relief provided by pregabalin. Additionally, the %MPE value of the group treated with 40 mg/kg rosmarinic acid showed a significant difference compared to the value of the pregabalin-treated group (P<0.001). Pre-administration of the antagonists revealed that the antiallodynic activity was shown to be mediated by the stimulation of opioid and adrenergic receptors, with a primary contribution from α2-adrenergic receptor stimulation. Our findings suggest that rosmarinic acid may hold promise as a potential therapeutic agent for neuropathic pain. By elucidating the involvement of adrenergic and opioidergic mechanisms, we have provided valuable preclinical data that could inform novel treatment approaches.