Effects of ionic products from silicon-substituted hydroxyapatite on the rat brain activity: Morris water maze studies and long term potentiation in hippocampal CA1

This study sets to examine the effects of ionic products from silicon-substituted hydroxyapatite (Si-HA) on brain activity in Wistar rats. Animals were treated intraperitoneally with leaching liquor of Si-HA once a day for 2 weeks. Morris water maze (MWM) test was employed to evaluate the spatial memory. The long term potentiation (LTP) of synaptic responses in the CA1 area was recorded. The expressions of growth associated protein-43 (GAP-43), glial fibrillary acidic protein (GFAP) and Nestin were identified by immunohistochemistry. The MWM test showed that the escape latency was markedly shortened by ionic products from Si-HA, meanwhile it produced a statistically significant improvement (p < 0.05) in the retention phase, implying a considerable improvement of spatial memory in Si-HA group. Moreover, LTP was significantly enhanced in Si-HA group as compared with that of control group. The GFAP expression was not upregulated in Si-HA group, but the expressions of GAP-43 and Nestin were increased. The findings suggested that there could be beneficial effects of Si-HA ionic products on rat brain function rather than to cause undesirable cerebral injury. The study provides the basis for further investigation into the biological applications of Si-HA.