| Objective: With the clinical application of the stereotatic radiosurgery technique (SRS) including Gamma Knife (GK) and X-knife, a lot of patients with diseases in the brain or in the cranial cavity can be treated by SRS instead of neurosurgical operations. Glioma is the most common malignant tumor among the intracranial neoplasms, and its incidence may reach up to about 40% of the all kinds of the brain tumors. The therapeutic effects of SRS on the brain glioma are definite which have been confirmed by many clinical reports. However after treatment of SRS most of the tumors would be relapsed, and some serious radiological reactions may occur, such as tumor necrosis and cerebral edema, etc. There have been some reports that cellular apoptosis could be evolved in the therapeutic effects of the GK, which could not result in serious inflammatory edema, and whether the cellular apoptosis would have some dynamic changes or not after radiation of GK in detail. Therefore it will be beneficial for preventing and relieving some radiological reactions of SRS that the cellular proliferation, apoptosis and necrosis could be realized in the pathological course after SRS.The rat with C6 glioma is a stable animal model for the brain glioma. At the first time (1992) Kondziolka used GK to treat the rats with C6 glioma in different radiological doses and observed the survival periods and pathological changes in those rats. The results were positive that the tumor volumes were reduced, the survival periods of the rats were prolonged, but the cellular necrosis and edema were also observed within their brains. Now it is well known that the cerebral edema is one of the maincomplications of SRS, which could result in high intracranial pressure, even in the cerebral hernia. The cerebral edema was caused not only by the direct effects of the irradiation, but also by the immune reactions within the brain, which was suspected by some studies. However, up to now there have been no reports on what the immune reactions would be occurred in the brain and the whole body after SRS treatment. Circumventricular organs (CVOs) are several miniorgans, which locate at the walls of the brain's ventricles, and include the subfornical organ (SFO),the median eminence(ME),the organum vasculosum of the lamina terminalis (OVLT), the subcommissural organ (SCO),the posterior lobe of the pituitary gland ,the area postrema (AP),and the choroid plexus. The major structural characteristics of CVOs are lack of the brain-blood-barriar (BBB). Until the nineties of the last century, the studies of CVOs had been mainly concentrated on their modulation on neuroendocrine aspects. However in the recent more than ten years, some studies have discovered that CVOs may take part in the roles of the immunoregulation, for example, many kinds of the receptors of the various cytokines may exist in CVOs. In the earlier period of 90 era of last century, Broadwell proposed the concept of " windows of the brain" as the "leaky points" in the brain barriar, which include the leptomenings and CVOs. However the homeostasis in the brain has been actually maintained in spite of the windows of the brain exist. And then some researchers suspected that the microglia may be enriched in CVOs and compensated as the immune barrier for some sites short of BBB. Why the windows of the brain would coexist with the brain barriers? In order to uncover this puzzle, a series of studies of CVOs on aspect of the neuroimmunoregulation have been carried out in our laboratory during about the last ten years. Among some our studies in the rats with the experimental allergic encephalomyelitis (EAE) the dynamic pathological changes of CVOs did occur in the different stages of EAE as a part of the systemic immune responses in the body. When different doses of lipopolysaccharide (LPS) were injected in the peritoneal cavity of the rat,the positive neurons of nitric oxide synthase expressed much more in SFO and had positive correlation with the doses of LPS. That may have suggested that...
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