The effect of silybin on passive avoidance learning and pathological changes in hippocampal CA1 and DG regions in male Wistar rats offspring

Abstract

Silybin, an extract from seeds of milk thistle (Silybum marianum), is known to have hepato-protective, anticarcinogenic, and estrogenic effects. Given that estrogen effects on memory have been reported, silybin may cause structural changes in the hippocampal CA1 and dentate gyrus (DG) neurons and as a result it may enhance learning and memory. Wistar rats were provided with silybin (from day 7 of gestational age up to 4 weeks after birth) with 2 dosages of 18 mg/kg in the experimental group 1 (Exp1) and 9 mg/kg in the experimental group 2 (Exp2). Offspring memory retention was compared by duration of step-through latency in passive avoidance apparatus. Furthermore, histological changes were investigated in experimental groups and control group (CG). Both the experimental groups showed significantly longer step-through latency than CG (p < 0.001 for Exp1 and p < 0.01 for Exp2). The average number of pyramidal cells in hippocampal CA1 and granular cells in hippocampal DG was remarkably higher in Exp1 and Exp2 compared with CG. The difference was significant between Exp1 and Exp2 for pyramidal cells (p < 0.05) but not for granular cells. Silybin administration during pregnancy resulted in histological changes in hippocampus and better memory function. These data may lay the ground work using silybin in memory impairment diseases.

Keywords:

• silybin
• passive avoidance learning
• Wistar rat
• hippocampus
• CA1
• dentate gyrus

Acknowledgements

We would like to express our gratitude to Dr Momeni, Dr Palizvan, and Mr Khazaei for their technical assistance and helpful discussion. The authors also wish to thank Dr Shahab Amini, Mr Kamran Amini, and Mr Masih Masoudi for their help, support, interest, and valuable hints.