Influence Of Superior Cervical Ganglionectomy Toneurogenesis In The Dentate Gyrus And Learning And Memory Of The Adult Rat

On the one hand,the cognitive science is one of the most rapid development and noticeable science in the life science aero.Along with neuroscience development,it is widely confirmed that neurogenesis is existence in rodents,primates and human. Many scholars thought that neurogenesis is along with the people's life in the dentate gyrus of hippocampal in adult.On the other hand,sympathetic nervous system is one of the important parts of the nervous system.Superior cervical ganglion(SCG)provides sympathetic input to the head and neck,it contains many neurotransmitters,such as the amines,amino acid and peptide etc.The neurotransmitters displayed different function respectively to carries on the precise regulation to the target organ to adapt organism demand.In addition,it,at present,has known that the SCG participate in the secrete of special neurotransmitters,rhythmicity regulation to blood pressure and so on.At the same time,some new functions are discovered unceasingly,but there also has the unknown physiological functions to be researched further.The present paper removed the SCG of adult rat to explore the influencing mechanism to mammalian learning,memory and neurogenesis in the dentate gyrus of adult rat when sympathetic nerve system was injured by accident,surgical procedure, or disease,especially superior cervical gangglionectomy,which provides the experimental data to sympathetic nervous system's clinical research.Rats were divided into three groups,bilateral(B SCGe group,n=10)and unilateral superior cervical ganglionectomy groups(U SCGe group,n=10)and the control(C group,n=10).Rats appeared Horner's syndrome after the surgery.Myosis, blepharoptosis,endophthalmos,hyponoia and frequency of take food and drink water was less in surgery groups than the control.The influence of surgery to rat learning and memory has been investigated by the methods of cue training in the Morris water maze.The result showed that all three groups' rats have obtained the reference memory to platform position in the navigation experiment,and finding strategy becomed from edge type to trend type or straight-line motion through 5-day training,and the latency decreased.The statistical analysis result indicated that B SCGe group's latency is higher than U SCGe and C group significant(P＜0.05),and there were no difference between U SCGe and C groups(P＞0.05).In the probe test,C and U SCGe groups' rats formed better memory to platform location,so their swimming track were mainly concentrated in the original platform position(the fourth quadrants),while B SCGe group rats crossed the others three quadrant more than C and U SCGe groups' rats.The platform was taken as the bull's eye,and the percentages of track in three groups' rats was counted in bull's eye and 9 round target.B SCGe group showed memory deficits,of which the performance was bad than the C and U SCGe groups,and memory score rate was lower significantly(P＜0.05).The neurogenesis in the dentate gyrus of hippocampal of adult rat has been examined after sugery by the methods of immunohistochemistry of doublecortin (DCX),a marker of neuron peogenetor cells.The result showed that the DCX-positive cells present brown granular cell,and the distribution in defferent regions(molecular layer,granular cell layer and subgranular zone)was heterogeneous.The DCX-positive cell's body located at subgranular zone or granular cell layer.The dendrites were orientated vertically and traversed both the granular cell layer,inner and middle molecular layers.The C group rats have many DCX-positive cells appearing cluster in SGZ.The U SCGe rats have fewer clustered DCX-positive cells.B SCGe group rats present dispersed DCX-positive cells.Through immunohistochemistry of DCX and quantitative analysis,the density of DCX-positive cells reduce extremely remarkable(P＜0.01)in C,U SCGe and B SCGe groups' rats.The above results suggested that C,U SCGe groups' rats have a better performance in Morris water maze than B SCGe group.The number and density of DCX-positive cells in dentate gyrus is more than B SCGe group.The reason is maybe that the contral ganglione has carried on some kind of functional compensation after unilateral ganglionectomy.Furthermore,the right superior cervical ganglion of adult rats was removed and the differences of shape,density and cell number of superior cervical ganglia was compared after contralateral ganglionectomy and normal superior cervical ganglia by light microscopy in adult rat.The experimental evidence was provided for the research of ganglion's impair.At the 30d,there were no difference in numerical density(Nv),number(N),volume density(Vv)and volume (Vn)in neurons between ganglionectomy and sham operation groups' rats.But there existenced extremely remarkable difference in Nv,N,Vv and Vn in non-neuronal cells between two groups(P＜0.01).Such conclusion would be got from above experimental result.It is that superior cervical ganglionectomy influence neurogenesis in the dentate gyrus of the adult rat in learning and memory,and bilateral ganglionectomy has a more remarkable influence. The reason is,maybe,that more than normal proliferation of satellite cells was to increase the activity of the controlateral ganglion after unilateral ganglionectomy.In addition,maybe leucocytic infiltration in the controlateral ganglion from outside the ganglion through immunological responses after unilateral ganglionectomy and then proceed some kind of compensatory immunity repair.