The definition of epigenetics and its cellular basis are introduced firstly in the paper. Then, the research progress on the relationship between cognition and epigenetic changes is re-viewed in detail. In conclusion, epigenetic modifications occur-ring in hippocampus, cortex and other brain areas such as methy-lation , phosphorylation , ubiquitination , poly ( ADP-ribos ) poly-merases and DNA methylation may certainly change animal be-haviors including learning, memory, synaptic plasticity, depres-sion, drug abuse and so on. Long-term memory and long-term potentiation( LTP) , activation of AMPK-ERK signal transduction path-way and activation of key gene regulated by CREB-ABP transcriptional complex as well as transcription and expression of memory and synaptic plasticity related genes ( Zif/268, Creb, Bdnf, reelin ) are required. In contrast, epigenetic abnormal changes such as histone and DNA hypomethylation and increase of HDAC activity are observed in brains of aging and neurodegen-erative diseases. Therefore, the main epigenetic treatments for cognitive impairments are increasing histone and DNA methyla-tion, using HDAC inhibitors and RNA interference ( RNAi) to promote formation of long term memory and long term potentia-tion, block learning and memory decline.

Ginseng has long been used as a tonic and agent for prolonging life span in chinese traditional medicine． Using morden technology，ginsenoside Rgl and Rbl were proved to be main active principles of ginseng．Both conpounds showed the same effect in improving learning and memory， increasing Bmax of M-cholinergic receptors and accelerating cerebral protein and acetylcholine biosynthesis．However，Rgl but not Rbl had immunoregulatory action in aged rats and anti-osteoporosis effect in ovariectomized rats as well as enhanced basic synaptic transmission and magnitude of LTP induced by HFS． On the other hand，Rbl had anti-stress effects in antagonizing acute,chronic and repeated stress induced reduction of sexual behaviour and decrease of plasma andogen or estrogen．Rgl showed no such effect even aggravate stress induced damage．Rhl possessed anti-oxidant activity and prolong survival time of mice in cold(－10℃) condition．There was no any anti-cold effect with Rgl .These diference of biological activities between Rgl and Rbl may be arributed to their structures containing different number of glucoses．

Melatonin (MT) is secreted by the pineal gland and has obvious biological rhythmicity including circadian, season rhythm and life rhythm (aging clock). The reduction of MT secretion is related to body aging, particularly in close relation to brain aging. The hypothesis of aging is involved in pineal calcification, biological clock, neuro-en-docrinoimmunology, and free radical damage. MT is an endogenous free radical scavenger, may anto-gonize the attack of hydroxyl free radical ( ?OH)on organism and glutamate (Glu) excitotoxicity, and has a potent protective effect of central nervous system. In vivo studies showed that the food restriction and exogenous MT could obviously prolong life, postpone aging, and reduce the chances of age-related diseases. Investigating of MT anti-aging effect shows a vast prospect.

Danshen-Radix Salviae Miltiorrhizae，is one of the common traditional Chinese medicines，which has been used clinically in the treatment of cardiovascular diseases more than 20 centuries.The active ingredients of Danshen has been researched 5 decades by the modern methods.Many researchers investigated the pharmacological effects of water soluble ingredients of Danshen-salvianolic acids in vivo and in vitro.The results demonstrated that salvianolic acids have different pharmacological effects such as potent antioxidative effects，scavenging free radicals，protect neural cells against injuries caused by anoxia， etc.In present paper，the pharmacological effects of salvianolic acids and the mechanisms of their actions are reviewed based on the research results obtained in our laboratory and other authors.

The growth associated protein(GAP 43) and neural cell adhesion molecule (NCAM) play an important role both in promoting neurite outgrowth and synaptic plasticity. GAP 43 is a neuron specific phosphoprotein that is highly expressed during the development of the central nervous system, nerve regeneration and the modulation of synaptic function, and it is frequently used as a marker for sprouting. GAP 43 may be involved in G protein interaction, membrane binding, calmodulin binding and protein kinase C phosphorylation. The various interactions, specified by the structural domains, are thought to underlie the role of GAP 43 in synaptic plasticity, participating in membrane extension during neuritogenesis, in neurotransmitter release and long term potentiation. NCAMs involve in the intracellular signaling cascades and stimulate the axonal growth, GAP 43 function is essential for NCAM stimulated neurite outgrowth and that much of this appears because of the phosphorylation of GAP 43 via the FGF receptor dependent stimulation of arachidonic acid. NCAM can accelerate the phosphorylation of GAP 43.

Stem cells exist not only in the developing mammalian embryo but also in certain areas of various adult tissues. In embryo, they can take part in the development of tissues and the whole organism while in adult, they are thought to be involved in cell metabolism. With the development of research in embryo and nervous system, the field of stem cells has become a hot point in scientific world. A brief summary is made on stem cell biology and its potential medical importance.

Microglia cells are immune cells in the central nervous system.When the microenvironment of brain has changed,microglia will respond rapidly.ATP,UTP,or other nucleotide signals released by neurons from damaged site and their metabolites such as ADP,adenosine,UDP and so on will bind with the purinergic receptors on microglia to regulate the morphology and function of microglia,then the microglial cells activated by nucleotide signals are to regulate neural cells by phagocytosis or releasing cytokines.In this article,the function and corresponding mechanisms of nucleotide signals on chemotaxis,phagocytosis,and process retraction are reviewed.

AIM To study the protective effect of total salvianolic acid against cerebral ischemia reperfusion injury. METHODS The cerebral ischemia reperfusion model in mice was made by means of ligating bilateral common carotid arteries in mice. After reperfusion, latency, error number of step down test and the gasping time after cutting head in ischemia reperfusion mice were recorded. Spectrophotometric assay were used to measure the activity of superoxide dismutase (SOD), the contents of malondialdehyde (MDA) and glutathione peroxidase (GSH) in brain of experimental mice brain homogenate. RESULTS In step down test, the ischemia reperfusion impaired the function of learning and memory in mice. The total salvianolic acid markedly improved the function of learning and memory, reduced the error number and extended the latency in ischemia reperfusion mice. The total salvianolic acid also significantly inhibited the changes of SOD, MDA and GSH in the cerebrum induced by ischemia reperfusion. CONCLUSION The total salvianolic acid has protective effects against cerebral ischemia reperfusion injury via its antioxidant activity.

Two aberrant structures, extracellular senile plaques (SP) and intracellular neurofibrillary tangles (NFTs) are the characteristic neuropathological hallmarks of Alzheimers disease (AD). Amyloid ? protein (A?) and hyperphosphorylated tau protein are the major components of SP and NFTs respectively. A large body of evidence has highlighted the pivotal role of sulfated polysaccharides in the amyloidogenesis and formation of NFTs. The underlying mechanisms of the involvement of sulfated polysaccharides in the development of AD were reported to contribute to their high affinity for both A? and tau protein. Sulfated polysaccharides not only promoted the ? secretase cleavage of APP and the increased production of A? and induced the aggregation and deposition of A?, but also facilitated the phosphylation of tau and promoted tau polymerization into fibrils and tangle formation. On the other hand, the neurotrophic effects exerted by sulfated polysaccharides were also demonstrated. These notions were probably due to the inhibition of the formation of A? fibrils or to the counteraction of the abnormal phosphorylation of tau by promoting the protein phosphatase2B activity, which has been speculated to be attributed to the variation in either structural backbone or degree of sulfation or position of sulfation. Putting together, the appropriate structural modification of sulfated polysaccharides may be effective as therapeutic agents for AD.

Object It was reported that salvianolic acid A from Salvia miltiorrhiza Bge could improve memory dysfunction of mice with cerebral ischemia reperfusion injury The effects of total salvianolic acids (Sal), including salvianolic acid A and B, rosmaric acid and protocatechic aldehyde was now studied to observe its effect on cerebral ischemia reperfusion injury in hope of obtaining a preliminary view on its mechanism of action Methods The effects of Sal on lactic dehydrogenase (LDH), superoxide dismutase (SOD) and malondialdehyde (MDA) of cerebral ischemia reperfusion injured mouse and rat models were observed Results Sal 10, 20 mg/kg iv and 5, 10 mg/kg iv could markedly increase the activities of LDH and SOD and lower the production of MDA in the injured cerebral tissue On focal cerebral ischemia reperfusion injured rat, 24 h reperfusion after 2 h ischemic injury, 5, 10 mg/kg iv Sal could decrease infarct size, ameliorate neurological deficit with obvious inhibition of the decrease of LDH and SOD activities and the over production of MDA Conclusion Sal showed obvious protective effects on cerebral ischemia reperfusion injuries of mice and rats via attenuating oxygen free radical