Background and aims: Rosmarinus Officinalis L. is a well-known plant with several useful properties such as analgesic and antiinflammatory. This study examines whether injection of muscarinic cholinergic (atropine, 20 µg/1 µl), µ1- opioid (naloxonazine, 20 µg/1 µl) or serotonergic (methysergide 20 µg/1 µl) receptors alters the antiallodynic effect evoked from the Rosmarinus Officinalis L. in neuropathic pain in mice. 
Methods: To induce neuropathic pain in mice, they were subjected to the chronic constriction injury, which consists in a transection of the peroneal and tibial branches of the sciatic nerve. The mechanic allodynia was evaluated using an electronic anesthesiometer (in 2, 7, 14 and 21 days after surgery). Drug and vehicle (saline) was administered intrathecally via a catheter implanted chronically in the space subarachnoid space. 
Results: The chronic constriction of nerve reduced the threshold for 30 days. Rosmarinus Officinalis L. injection (250mg/Kg, intraperitoneal) reduces the severity of neuropathic pain induced by chronic constriction injury during initial (2 days following the injury, 50%) and maintenance (subsequent 7 days, 70%) phase. On the other hand, Intratecal naloxonazine, but not atropine, methysergide or saline fully inhibited the Rosmarinus Officinalis L.- induced antiallodynia. 
Conclusion: We conclude µ1- opioid receptors are involved in the antiallodynic effect evoked from Rosmarinus Officinalis L.

µ1- OPIOID RECEPTORS MEDIATE THE ANTIALLODYNIC EFFECT OF ROSMARINUS OFFICINALIS L. (ALECRIM) IN NEUROATHIC PAIN IN MICE