AMELIORATIVE EFFECTS OF ANGIOTENSIN RECEPTOR BLOCKERS AGAINST SCOPOLAMINE-INDUCED MEMORY IMPAIRMENT IN RATS

ABSTRACTObjective: The present study was designed to investigate the cognitive enhancing property of angiotensin receptor blockers (ARBs) in scopolamineinducedamnesic rats.Methods: A total of 42 male Wistar rats were divided into seven groups. Group 1 received 2% gum acacia orally for 4 weeks, Group 2 received normalsaline, and Group 3 received scopolamine (2 mg/kg/i.p.) as a single dose. Groups 4 and 5 received telmisartan (1.80 mg/kg and 3.60 mg/kg, respectively)while Groups 6 and 7 received losartan (2.25 mg/kg and 4.50 mg/kg, respectively), orally for 4 weeks, followed by scopolamine (2 mg/kg/i.p.) given45 minutes prior to experimental procedure. Evaluation of learning and memory was assessed by using morris water maze test followed by estimationof hippocampal choline acetyltransferase (ChAT) activity. Alterations in hippocampal morphology and degree of neuronal survival were also analyzedfollowing drug treatments.Results: Scopolamine-induced marked impairment of memory in the behavioral test which correlated with reduced ChAT activity and morphologicalchanges in the hippocampus. Treatment with higher doses of telmisartan and losartan improved memory deficits in scopolamine-induced amnesicrats while increasing the hippocampal ChAT activity. The treatments also attenuated hippocampal degeneration and increased the number of survivingneurons in hippocampus scopolamine-induced amnesic rats.Conclusion: Pre-treatment with ARBs attenuated scopolamine-induced memory deficits which may be attributed to their angiotensin receptorblockade property or to improved cholinergic activity, and thus highlighting the potential of these drugs in dementia.Keywords: Angiotensin scopolamine, Amnesia, Angiotensin receptor blockers, Losartan, telmisarta