Effects Of Ginsinoside Rd On Neurogenesis In The Dentate Gyrus Of Normal And Infrasound-exposed Adult Rats

Ginsenoside is one of the effective ingredients in ginseng.At present,more than 40 kinds of ingredients have been separated from ginsenoside.As one of the most important ingredients,ginsenoside Rd shares many pharmacological effects.Ginsenoside can facilitate the acquirement,consolidation and reappearance of learning and memory,and improve neural plasticity.It is said that the learning and memory ability of adult animals has close relation to neurogenesis in the dentate gyrus,so it is possible that ginsenoside Rd can affect the process of neurogenesis.Neurogenesis is defined as the process of proliferation,survival and differentiation of NSCs.Recently,it has been investigated that,neurogenesis exists in the brain of many kinds of adult animals,including mammals,and new neurons and glial cells are generated through this process.Dentate gyrus is one of the regions being studied most.It is said that the neurogenesis in adult hippocampus participates in the formation of learning.In our experiment,to study the effects of ginsenoside Rd on neurogenesis,ginsenoside Rd in different dosage was given intraperitoneally to normal rats,then the proliferation, differentiation and migration of NSCs in SGZ was observed by immunostaining at different time after Rd treatment.Many environmental factors affect the level of neurogenesis.We have investigated that infrasound of 8 Hz at 130 dB can inhibit the proliferation of NSCs in normal adult rat SGZ.Infrasound is usually defined as the sound with frequeny below 20 Hz,which comes from mechanical vibration.A large variety of natural and man-made phenomena can produce infrasound.Infrasound at high intensity does harm to our bodies and plays an important role in noise pollution.As a significant target organ,brain is very sensitive to infrasonic damage.Experimental studies have reported that many parts of brain changed after infrasound exposure in some aspects,such as structure,function and neurotransmitter metabolism.This process is complicated and has special mechanism of action.In our study,we observed the effects of ginsenoside Rd on neurogenesis in SGZ in rat brain after infrasound exposure to investigate the safety action of ginsenoside Rd to infrasound injury and to provide experimental evidence for the prevention and cure research of infrasound.Experiments were carried out to observe the effects of ginsenoside Rd on neurogenesis in the dentate gyrus of normal and infrasound-exposed adult rats. Experiment 1:Adult normal male Sprague-Dawley(SD)rats were treated intraperitoneally with ginsenoside Rd and killed at different time after that. Before the rats were sacrificed,three pulses of BrdU were given intraperitoneally to label the S-phase cells,which were detected by anti-BrdU immunostaining.Rats killed at 3 d,7 d and 14 d were used to observe the proliferation of NSCs,and those killed at 34 d were used to observe the differentiation and migration of NSCs.Experiment 2:Adult male SD rats were randomly divided into a normal control group,a sham control group,an infrasound group and a infrasound+ginsenoside Rd group.Rats of the infrasound group and the infrasound+ginsenoside Rd group were exposed to infrasound of 16 Hz at 130 dB for 2 h/d in 7 consecutive days.Observation was carried out after infrasound exposure and the method was identical to experiment 1.The results are showed as follows:1.Effects of ginsenoside Rd on the proliferation of NSCs:BrdU positive cells in each group appeared as irregular shaped single or clusters located exclusively in the SGZ.Experiment 1:3 d and 7 d after Rd treatment,BrdU positive cells increased markedly,but the number of dividing cells appeared to return to control levels at 14 d after Rd treatment.Experiment 2:After Rd treatment,BrdU-positive cells were significantly increased in the SGZ at 3 d after infrasound exposure,compared with those of the infrasound group,and the difference was more obvious at 7 d.However,14 d after infrasound exposure,a large number of BrdU-positive cells were reappeared in the infrasound group,and the difference disappears accordingly.2.Effects of ginsenoside Rd on the differentiation of NSCs:From the double labeling immunostaining,we found in each group the percentage of NeuN-expressing BrdU immunoreactive cells is about 70%.However,the BrdU labeled cells scarcely expressed astrocyte markers.So,there is no influence of ginsenoside Rd on the differentiation of NSC.3.Effects of ginsenoside Rd on the migration of NSCs:At 34 d treatment group,the location of BrdU positive cells changed.Some of the cells were still in the SGZ,but many were found throughout the GCL.There was also a marked change in the morphology of BrdU positive cells.By the 34 d,most nuclei in the SGZ and GCL appeared much bigger and round,just like those of surrounding granule neurons.After Rd and infrasound treatment,there was no ectopic granule cell migration.The following is the conclusion of our experiments:Ginsenoside Rd markedly increases the neurogenesis in the dentate gyrus of normal and infrasound-exposed adult rats,and the differentiation and migration of new NSCs are not affected after Rd treatment and infrasound exposure.