Background & aim: Silver nanoparticles (Ag NPs) have been widely used in many technologies to produce medical devices, food technology and textiles. Silver nanoparticles may be absorbed through the lungs and intestine into circulation and thus may reach such organs as the liver, kidney, spleen, heart and testes and brain. It has been demonstrated that silver nanoparticles may have toxic effects on mammalian cells. There are some alarming reports on the adverse effects of silver nanoparticles on reproduction of experimental animals. Exposure to silver nanoparticles may exert a neurotoxic effect and affect cognitive functions, causing the impairment of short-term and working memory. The purpose of this study was to investigate the possible protective role of Ag NP on the learning and memory of rats.

Methods: The present experimental study was conducted on forty male Wistar rats weighing 200 to 250 g which were divided into five groups of eight as follows: control group and 4 groups of treatment. Control group rats received saline and treatment group’s rats received Ag NP at doses of 50, 250,500 and 1000 mg/ kg/ day using Intra Peritoneal injection (IP) for 14 days. One day after the last injection, the learning and memory function in the rats was examined by the passive avoidance task. Measure of memory and learning were assessed using One-Way ANOVA by SPSS using the  Tukey s' test.

Results: The results showed that Ag NP at dose of 50, 250, 500 mg/kg made no significant change in the STL (step-through latency) and TDC (Time in Dark Compartment), compared to the control group in the passive avoidance task. Despite, Ag NP at dose of 1000 mg/kg significantly reduced the STL (p<0.01) and increased TDC (p<0.001), but no significant change in the number of trials (p>0.05) compared to the control group.

Conclusion: These data suggest that ip microinjection of Ag NP could impair learning and memory at high doses.