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

In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: a b s t r a c t a r t i c l e i n f o Keywords: Silicon-substituted hydroxyapatite Long-term potentiation Morris water maze GFAP GAP-43 Biocompatibility 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 immunohistochem-istry. 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 b 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. Synthetic hydroxyapatite (HA) with a chemical composition of Ca 10 (PO 4) 6-(OH) 2 has been widely used clinically as bone graft or coating on metallic prosthesis in joint replacement due to its excellent biocompatibility and bioactivity [1]. However, the reactivity of HA implants is relatively low in comparison with bioactive glasses and glass ceramics, which can lead to a low bone apposition rate [2] and a prolong time period for patient rehabilitation. Although silicon has only been found in trace quantities in bone mineral, it has been shown to have a crucial role in bone formation and calcification, and believed to be essential in skeletal development [3,4]. The silicon-substituted HA (Si-HA), a chemically modified apatite, has emerged for bone tissue engineering and next generation bioactive coatings [5]. Several findings indicated that the in vivo and in vitro bioactivity of …