Systemic Kainic Acid (KA) administration has been used to induce experimental temporal lobe epilepsy in rats. The aim of this study was to evaluate the neuroprotective effect of rosemary extract (RE, 40% Carnosic acid) against KA-induced neurotoxicity in hippocampus and impaired learning and memory. Animals received a single dose of KA (9.5 mg/kg) intraperitoneally (i.p.) (KA group) and were observed for 2 h and were scored from 0 (for normal, no convulsion) to 5 (for continuous generalized limbic seizures). RE (100 mg/kg, orally) was administered daily for 23 days, starting a week before KA injection (KA+RE group). Neuronal degeneration in hippocampus was demonstrated by using Fluoro-Jade B immunofluorescence. The number of pyramidal cells in hippocampus was evaluated by Nissl staining. Also, the Morris Water Maze and Shuttle box have been used to assess spatial memory and passive avoidance learning, respectively. Our results revealed that, after treatment with RE, neuronal loss in CA1 decreased significantly in the animals in KA+RE group. The Morris water navigation task results revealed that spatial memory impairment decreased in the animals in KA+RE group. Furthermore, results in Shuttle box test showed that passive avoidance learning impairment significantly, upgraded in the animals in KA+RE group. These results suggest that RE may improve the spatial and working memory deficits and also neuronal degeneration induced by toxicity of KA in the rat hippocampus, due to its antioxidant activities.

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Systemic kainic acid administration has been used to induce experimental temporal lobe epilepsy in rats. The aim was to evaluate the neuroprotective effect of rosemary extract (40% Carnosic acid) against kainic acid-induced neurotoxicity in hippocampus and impaired learning and memory. Subjects received a single dose of kainic acid (9.5 mg/kg) intraperitoneally, were observed for two hours, and scored from 0 (for normal, no convulsion) to five (for continuous generalized limbic seizures). Rosemary extract (100 mg/kg, orally) was administered daily for 23 days, starting a week before kainic acid injection. Neuronal degeneration in hippocampus was demonstrated by using Fluoro-Jade B immunofluorescence. The number of pyramidal cells in hippocampus was evaluated by Nissl staining. Also, the Morris water maze and shuttle box were used to assess spatial memory and passive avoidance learning, respectively. Results revealed that, after treatment with rosemary extract, neuronal loss in CA1 decreased significantly in subjects in the kainic acid + rosemary extract group. Morris water navigation task results revealed that spatial memory impairment decreased in subjects in the kainic acid + rosemary extract group. Furthermore, results in shuttle box testing showed that passive avoidance learning impairment significantly improved for subjects in the kainic acid + rosemary extract group. These results suggest that rosemary extract improves spatial and working memory deficits and also, due to its antioxidant activities, neuronal degeneration induced by the toxicity of kainic acid in rat hippocampus.

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