RESUMO
Silymarin, an extract from seeds of milk thistle [Silybum marianum], is known to have hepato-protective, anticarcinogenic, antioxidant and estrogenic effects. The aim of the present study was to test the effect of silymarin on passive avoidance learning in rats. This was an experimental study carried on Wistar rats in Arak Unviersity, Iran. The animals were provided with silymarin [from day 7 of gestational age to 4 weeks after birth] at 2 doses of 180 mg/kg in the experimental group 1 [Exp 1] and 90mg/kg in the experimental group 2 [Exp 2] while the sham group received saline and the control group with regular food and water. The memory retention and duration of step-through latency in male offsprings was determined by passive avoidance apparatus. Neuronal density in hippocampus was established by histopathological value less than 0.05 was considered as significant. Both experimental groups showed significantly longer step-through latency compared to control group [p<0.05]. The average number of pyramidal cells in hippocampal CA1 and granular cells in the hippocampal DG were remarkably higher in Exp 1 and Exp 2 groups compared to control group. The difference between Exp 1 and Exp2 for pyramidal cells was found to be significant [p<0.01 and p<0.05, respectively]. Silymarin produced a significant increase in learning and memory. Also, our results indicate that silymarin is a dose dependent component. These data may lay a background for application of silybin in treatment of memory impairment diseases