The Effect Of Magnetic Stimulation Of Different Intensities On The Expression Of Fos Protein In Neurons Of Pigeon’s Spinal Cord And Brain

The biological effects of magnetic field has been widespread concerned. It had been studiedin multiple levels of molecules, cells, tissues, and individuals. The nervous system is especiallysensitive to magnetic stimulation reaction. On the influence of magnetic field on the pigeon,people mainly focused on its effect on the geomagnetic navigation. Researchers recently usedFos protein as index to explore the effects of magnetic field on the neuronal activity.But theresearches were only focused on the pigeon’s retina and vestibular nucleus.It had not beenreported in other parts of pigeon’s.The first part of this study is to screen out the best stainingmethod of neurons in spinal cord and brain.Then,the verified experiment on the general structureof the pigeon’s spinal cord was done.The main part of this study is to explore the effect ofmagnetic stimulation on neuronal activity of the spinal cord and brain by giving differentpermanent magnetic stimulation to pigeons, using molecular immunohistochemical techniquewhich used Fos protein as an index. The purpose of this research is to provide experimental basisfor the study of physiological mechanism of pigeon navigation.The research was divided into four parts:1.The comparison of different method to display the morphology of hippocampalneurons: The frozen sections from pigeons’ brains were stained with neutral red,methyleneblue,cresyl violet,haematoxylin-eosin(HE), and Cajal’s staining method respectively,thencompared the morphology of hippocampal neurons.Results indicate that there are differencesamong the five kinds of staining methods and the cresyl violet staining method is the best one ofthem.2. The general structure of the spinal cord: The pigeons(Columbiformes, Columbidae,Columba,n=18) buying from market were killed by excessive anesthetic and perfused forfixation through heart. They were divided into the group of gross anatomy macroscopicobservation, the group of the spinal transection observed by binocular dissecting microscopeand the group of the spinal cord made into frozen transection, stained with cresyl violet, observed by optical microscope.The result displays that there are38segments of the spinal cord.According to these locations and structures,they can be divided into five parts:the cervical,thoracic, lumbar, sacral and tail. The dorsal median suleus of the lumbosacral spinal cord isbroadened, It is called second rhomboid fossa., and has the glycogen body at the bottom. Thecell bodies of the neurons in white matter of the cervical and lumbosacral spinal cord gather intonerve nucleus.3. The effects of different intensity permanent magnetic stimulation on the expressionof Fos protein in neurons of the spinal cord:The normal adult pigeons (300~400g bodyweight)were randomly divided into control group (no treatment) and experimental group. Theexperimental group was divided into five groups with5pigeons in each group, respectively:group1: the members were carried magnet A (weight6.98g, magnetic field strength of220mT)on their back; group two: the pigeons were carried a bag of corn on their back(weight6.98g); Group Three: the pigeons were carried magnet A and be anesthetized; group four: themembers were carried a bag of corn(weight6.98g) and be anesthetized; group five:they werecarried magnet B (weight4.31g, the magnetic field strength of157mT)on their back; group six:they ere carried magnet C (weight3.91g, the magnetic field strength of192mT)on their back.Then, all animals were allowed to survive for1hour in the waking state and could behavior atease.The group3and4were injectioned with anesthetic(procaine hydrochloride) twice(1minand30min).Then the animals were killed by overdose anesthesia and perfused for fixationthrough heart.The spinal cords of them were made into frozen sections and then were handledwith Immunohistochemical technique.We observed and photographed using lightmicroscope,couted the number of Fos immunoreactive neurons in each group. Results showedThe number of Fos protein immunoreactive (Fos-IR)positive neurons in the spinal cord of eachsegment which were in the experimental group were significantly more than those of the controlgroup (P<0.05); the number of the Fos-IR positive neurons in the spinal cord of each segment inthe experimental group three were significantly more than those of the group four (P<0.05).Itindicates that the weight-bearing stimulation(3.91~6.98g)and magnetic stimulation(157mT~220mT) both can strengthen the expression of Fos protein in spinal cord neurons; Chest and back(permanent magnet contact position) subcutaneous, muscle injection of Procaine(a localanesthetic) can effectively block the expression of Fos protein which was induced by load, while the expression of Fos protein induced by magnetic stimulation can’t be blocked.Therefore,themagnetic stimulation of157mT~220mT can strengthen the neuronal activity; the stimulationmay be a direct effect on neurons induced by magnetic field.4. The effects of different intensity permanent magnetic stimulation on the expressionof Fos protein in neurons of the hippocampus and area parahippocampalis:The methods ofanimal grouping, immunohistochemistry and observation were all the same as section3,exceptthat the experimental object was pigeon’s brain. Results indicated that the number of the Fos-IRpositive neurons in the hippocampus(HP) and area parahippocampalis(APH) which were in theexperimental group were significantly more than those of the control group (P<0.05); there weremore the number of the Fos-IR positive neurons in the experimental group three than those of thegroup four (P<0.05).It indicates that the weight-bearing stimulation(3.91~6.98g)and magneticstimulation(157mT~220mT) both can strengthen the expression of Fos protein in HP and APH;Chest and back (permanent magnet contact position) subcutaneous, muscle injection of Procainecan effectively reduce the expression of Fos protein which was induced by load, while is lesseffect is of the expression of Fos protein induced by magnetic stimulation.In summary, thisexperimental study demonstrated that, the weight-bearing stimulation (3.91~6.98g)and magneticstimulation(157mT~220mT) both can enhanced the expression of Fos protein in the spinal cord,HP and APH. Peripheral nerve local anaesthesia only can effectively inhibit the neuronal activityinduced by loading, not obvious on magnetic stimulation induced effect. The results suggest thatthe magnetic lines of force maybe directly act on the gray matter of the spinal cord neurons toreinforce its activity; the enhance of activity in the HP and APH may be associated with theinformation uploaded by the spinal cord. The molecular mechanism which the magnetic field caninduce the neuronal activity should be further explored.