The Ultrastructural Changes Of Synapse And The Expression Of Synaptophysin Following Focal Cerebral Ischemia In Rats

Objective: UsingHEstaining,Nisslstaining ,immunohis-tochemistry staining technique and electronic microscope,a focal cerebral ischemia rat model was made in order to study the ultrastructural changes of synapse and the expression of synaptophysin following focal cerebral ischemia in rats.We expected to understand the relationship between cerebral ischemia and synapse .By this study we could establish a new method to study the brain plasticity after cerebral ischemia.Materials and Methods: Experiments were performed on health SD rats,male or female,weighing 280-300g.Cerebral ischemia was induced by permanently occluding the distal middle cerebral artery.At 4h,24h,48h after operation(n=10),the rats were anaesthetized with ether,heads were transsected and the cerebral parietal cortex were removed.Brain tissues were taken with 4% polyformaldehyde embedded with paraffin and sectioned as usuaJ.Methods of light microscope.electron microscope and immunohistochemistry were involved in this study.Results: l.HE staining and Nissl stainingiln control group the neuron in cerebral partietal cortex were distributedin 6 layers(ie.molecular layer,external granular layer,external pyramidal layer,internal granular layer, internal pyramidal layer.and polymorphic layer) .The neurons were dense and lined tidily.Cells were in normal shape and the number was numerous.Neucleus were large and spherical. 4h postischemia, the pathological changes were slight: the soma slightly swollen,some unusual vesicle degeneration appeared in plasma.Nissl bodies decresed.24h postischemia,neuronal damage was signifcant.The structure of the cerebral parietal cortex became abnormal.Neurous were distributed irreguarly with small cell bodies.There was a blank area between cell and tissue.48h postischemia,a number of neurons died.A pile of neurons were loss.Neurons were abnormal in shape and became multiangular or triangular.Nucleolus pyknosis with intensive staining.Vacuolar degeneration was observed in cell bodies.2.Bax:In control group,Bax protein has no expression in cerebral parietal cortex neurons., Bax immunoreactive positive cells in ischemia area increased slightly At 4h postischemia(The number of Bax immunoreactive positive cells was 1.26+0.67,P<0.05) .24h postischemia,the number of positive neurons increased apparently(The number of Bax immunoreactive positive cells was 15.62+2.32,P<0.01) .48h postischemia,the Bax protein expression increased significantly and the positive neurons were all over the field(The number of Bax immunoreactive positive cells was27.93+3.18,P<0.01) .Bax protein positive staining mainly in cytoplasm and could also be seen in nucleolus. 3.Synaptophysin:In control group,synaptophysin immunor-eactive positive products were observed.They were brown granules or dots with intensive staining and distributed not only between neurons but around the neurons also.Sometimes posisive punctate products outlined the main profile of the neurons.The nucleus,the cell bodies and the glial cells had no positive products and capillary could not be seen stained (the optical density(OD)of synaptophysin positive products was45.14+3.89). 4h postischemia,synaptophysin positive products decresed shghtly(the optical density(OD)of synaptophysin positive products was40.96+4.32, P<0.05).24h postischemia, synaptophysin positive products decresed distinctiy.The positive granules which around the neurons were disappear(the optical density(OD)of synaptophysin positive products was!4.16+2.76, P<0.01).48h postischemia,many neurons died and vacuolar degeneration was observed in cell bodies.Synaptophysin positive products decreased significantly (the optical density(OD)of synaptophysin positive products was7.89+2.86, P<0.01). 4.Ultrastructure:4.1Neurons:In control group,cells were hi normal shape.Neucleus were large and spherical. A number of cell organells were seen(ie.Golgicomplex,mitochondria,rough endoplasmicreticulum).4h after ischemia,mitochondria swollen slightly.Some of mitochondria cristas dissolved and broken,endoplasmic re...