Results of systematic review and meta-analysis showed that dexamethasone used as adjunctive local anesthetic when administered by perineural pathway prolonged the duration of block sensory / analgesia. Some authors have described that dexamethasone, regardless of the route of administration (intravenous or epidural), had prolonged duration of analgesia block of interscalene with ropivacaína. Still found an increase in the duration of analgesia when the drug was used by epidural route in sciatic nerve blockade, similar to that with dexamethasone used intravenously. Iodinated contrast media, corticosteroids administered in the epidural space and spinal, trauma, blood, chemotherapeutic agents, preservatives and preservatives contained in many solutions, contaminants such as detergents and even local anesthetics were associated with arachnoiditis adhesive. Subarachnoid injection of betamethasone and methylprednisolone triggered adhesive arachnoiditis in dogs. In rabbits epidural injection of methylprednisolone did not cause histological changes in meninges44. In rat spinal injection of triamcinolone through chronically implanted catheter, caused no histological changes in nervous tissue and did not evaluate the meninges. The objective of this study is to evaluate histological effects of dexamethasone administered in the subarachnoid space, determines nervous tissue of the spinal cord and meninges of rabbits. Method- 20 young adult rabbits, weighing between 3000 g and 5000 g and spinal cord between 38 and 40 cm provided by the animal house of the Campus of Botucatu, Universidade Estadual Paulista "Júlio de Mesquita Filho" will be used. The selection of those animals will be excluded if they fail to look healthy and they will be divided into 2 groups (G): G1 with 0.9% saline, dexamethasone 0.37 mg.kg-1. After 12 h of fasting with free access to water the animals will be anesthetized with ketamine and xylazine spinal puncture and subjected to administration of a solution of the previously drawn. After recovery from intravenous anesthesia and during 21 days of captivity they will be evaluated for motility and pain perception. After that, they will be sacrificed by decapitation under intravenous anesthesia and removed the lumbar and sacral portion of the spinal cord and meninges for histological examination with HE and GFAP.
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