Resumo

Objectives: Neurons containing agmatine are located in brain areas associated with the control of several important functions, such as visceral and neuroendocrine control, processing of emotions, pain perception and cognition. Due to the abundance of agmatine in the hippocampus, some recent studies have investigated the role of agmatine on learning and memory processes. The main objective of this study was to evaluate the effects of the exogenous administration of agmatine in the short- and long-term spatial memory impairments induced by aging and scopolamine in rats. Materials and methods: a total of 40 male Wistar rats with 3 months-old (young group) and 25 male Wistar rats with 15 months-old (aged group) were used in this study. A single administration of scopolamine (1 mg ⁄kg) by intraperitoneal (i.p.) route was done only in the young group 30 minutes before the behavioral tests. Scopolamine transiently impairs cognitive functions through the blockage of muscarinic acetylcholine receptors. Agmatine (10, 50 or 100 mg ⁄kg, i.p.) was administered acutely 15 min before the behavioral tests, that included activity cages and the step-down inhibitory avoidance task for the evaluation of locomotor activity (30 min) and short- (1.5 h) and long-term (24 h) spatial learning and memory, respectively. Results: Acute treatment with agmatine did not reverse the learning and memory impairments induced by scopolamine in rats. On the other hand, the i.p. treatment with agmatine, at doses of 10 and 50 mg ⁄kg, improved the age-related short- and long-term memory impairments observed in the step-down [latency to step-down (s) cont: test1.5h: median:101,8 25%percentile:27,5 75%percentile:176,0; test24h: median:92,0 25%percentile:8,0; 75%percentile:176,0; Agmatine10: test1,5h: median:108,0; 25%percentile:40,0; 75%percentile:176,0⁄ test 24h: median:100,3; 25%percentile:32,5; 75%percentile:168,0; Agmatine50: test1,5h: median:109,0; 25%percentile:45,0; 75%percentile:173,0 ⁄ test 24h: median:93,0; 25%percentile:35,0; 75%percentile:151,0]. Although aging and the scopolamine treatment did not alter per se the locomotor activity of the animals, the administration of the intermediary tested dose of agmatine (50 mg ⁄kg, i.p.) reduced the locomotor activity of aging rats in the activity chambers [crossings: cont: 143,6 &#+17717,2; Agmatine10:97,8 &#+17721,0; Agmatine50:52,5 &#+17712,8; Agmatine100: 83,6 &#+17720,6]. Conclusions: The present findings indicate that the acute treatment with agmatine improves age-related short- and long-term memory impairments in rats and that this response seems to be independent of its action in the cholinergic system. Financial support: CNPq, CAPES CEUA/UFSC: PP358