Investigação do potencial uso do Modafinil como agente melhorador da memória

Abstract

Modafinil is a drug that promotes increased alertness. It was approved for the treatment of excessive daytime sleepness in narcolepsy and obstructive sleep apnea. Some studies indicate that Modafinil can improve learning, memory and reverse cognitive loss induced by sleep deprivation and stress. This study was aimed to characterize the effects of modafinil on control adult rat s memory. Further, its effects were also studied using three models of cognitive decline to assess modafinil effects on memory. The iron overload model on neonatal period related to the degenerative diseases, maternal deprivation on neonatal period that generates emotional and cognitive impairment on adulthood, and, paradoxal sleep deprivation, which is known to interfere with on memory consolidation. The first experiment investigated the effects of the drug on memory consolidation and retrieval using distinct paradigms of learning; object recognition and inhibitory avoidance (aversive memory task) in healthy adult rats. Male Wistar rats received a single injection of acute modafinil (0.0; 0.75; 7.5 or 75 mg/kg) immediately after training or one hour before object recognition or inhibitory avoidance retention tests. Acute administration of modafinil to healthy rats did not affect memory consolidation or retrieval. The second experiment examined the acute or chronic administration of modafinil on the reversal of memory deficits induced by iron overload in the neonatal period, a model of cognitive decline related to neurodegenerative disorders. Rats treated with iron between 12 and 14 postnatal days received in adulthood, acute intraperitoneal injection of modafinil (0.0; 0.75; 7.5 and 75 mg/kg) immediately after training in the recognition task object. A single injection of modafinil at the highest dose was able to recover recognition memory in rats treated with iron. In order to investigate the effects of chronic treatment with modafinil, irontreated rats received intraperitoneal injections of modafinil at the same doses for seventeen days. Twenty-four hours after the last injection, the animals were submitted to object recognition or inhibitory avoidance training. Memory retention tests were performed twenty four hours after training. Chronic administration of modafinil fully recovered memory deficits induced by iron both in recognition memory and emotional memory. Experiment III evaluated the effects of maternal deprivation combined with paradoxical sleep deprivation (PSP) on recognition memory. Wistar rats separated from their mothers for fourteen days, three hours per day, underwent PSP for twenty four hours in adulthood. The model allowed to investigate the ability to reverse such deficits with administration of modafinil that was effective in restoring cognitive decline caused by maternal deprivation and PSP. The use and commercialization of modafinil as a stimulant is widely proved. To support its application in the memory loss associated with neurodegenerative disorders, stress in early life and PSP, additional preclinical and clinical research are needed. This study shows, however, through the proposed models of cognitive decline, the drug effectiveness in reversing such memory deficits.