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.

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.

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.

Purpose　The aim is to study the activity and the sildenafil selective inhibition of PDE5. Methods　The PDE isoenzymes were purified from bovine penis corpus cavernosum tissue by FPLC system. PDE activity was assayed by using 3　H-cGMP as substrate, the PDE isoenzymes hydrolyzed it to 3　H-GMP, and 3　H-GMP was further hydrolyzed to 3　H-guanosine by 5′-nuclease of snake venom. Add scintillation cocktail to observe the PDE isoenzymes activity. The selective inhibitor sildenafil of different concentrations were used to observe the inhibition of PDE5. Data replotted according to procedure of Dixon plots.Results　Three PDE isoenzyme peaks were purificated from bovine corpus cavernosum. The PDE of the third peak had the strongest activity of cGMP hydrolyzation which could be inhibited by sildenafil apparently.Conclusion　Since PDE5 was mainly found in corpus cavernosum tissue of mammalian, and sildenafil was a selective inhibitor of PDE5. It was suggested that the third peak was PDE5. The result was in agreement with the article reported.

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 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 effect against cerebral ischemia reperfusion injury via its antioxidant activity.

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.