The Effect Of Low-Dose Gamma-Knife Radiation On The Glutamate And γ-amino Butyric Acid In Hippocampus Of Experimental Epileptic Rats

Epilepsy is a set of clinical syndromes, which is characterized by transient disorder of cerebral function and caused by suddenly and recurrently seizure of neuron in brain, and there are a series of physiological and pathological changes including cerebral blood flow,metabolism,neurotransmitters and so on. It is the highest incidence of the disease in nervous system except of cerebrovascular diseases. The incidence rate is 0.5%-1.0%. Of which 25% were drug refractory epilepsy. It affects the normal life of patients seriously. There are about 9 million epileptic patients in our country. Epileptic patients and their families in social life, are under enormous psychological pressure. It has brought a heavy burden to a medicine, family and community.So far, the mechanism of epilepsy has not been fully uncovered. Nevertheless Many experts of epilepsy have generally accepted that there are two important characters of epilepsy's:the increase of neuronal excitability and the firing of highly synchronization. Glutamate (Glu) is the major excitatory amino acid neurotransmitter in brain. More than 50% neurotransmitter of synapses is Glu. Almost the excitatory neurons are glutamatergic neurons. It is crucial that Glu maintains the normal excitability of neurons. However, excessive accumulation of Glu in the extracellular could lead to convulsion.γ-amino butyric acid (GABA) is the most important inhibitory neurotransmitter in the central nervous system, and plays a crucial role in blocking the proliferation and transmission of excitement. Reduced synthesis of GABA may result in that excitement of neurons is out of control, leading to the onset of epilepsy.At present, the main method of controlling epilepsy is to use chemicals. However, the mainly used anti-epileptic drugs (AEDs) can only control about 70 to 80 percent the seizure. While the side effects of AEDs accompanied with long term administration are serious. As the development of medical imaging technology and Electrophysiology, positioning of the epileptogenic focus has become more and more accurate, and surgical treatment has become an important means of intractable epilepsy. But the risk of surgery can not be avoided. In addition to regular neurosurgical craniotomy complications such as bleeding, infection, limb motor dysfunction, cranial nerve dysfunction, etc. Mental or emotional abnormalities, language dysfunction, mental and memory decline, etc, may also occur. The incidence is 0.5%～20.0%. It is necessary to explore a more effective and safe method of treatment.Gamma Knife radio surgery is a minimally invasive, safe and accurate positioning treatment, and has the advantage of repeatability. In a small volume, concentrated, precise high-dose radiation will not cause damage on the surrounding brain tissue of target point, and a minor effect on nerve function. The safety and efficacy in animal experiments and clinical studies had already been reported. More importantly, patients with short hospital stay and quick recovery, low cost, and it will not affect their quality of life. Over the past 10 years, the application of low-dose exposure to epilepsy was gradually increased. Most scholars believe that the dose of 10Gy irradiation does not produce a small area of brain necrosis. Seizures can be controlled without complications. To further study the anti-epilepsy of low-dose irradiation and to explore whether the anti-epilepsy of low-dose irradiation is obtained by regulating the excitatory and inhibitory neurotransmitter, the effect of low-dose irradiation on Glu and GABA in hippocampus of epileptic rats induced by li-pilocapine.Then discuss the antiepileptic mechanism of low-dose irradiation in the level of the neurotransmitter, to provide a theoretical basis for Gamma Knife treatment of epilepsy.105 healthy adult male Wistar rats of SPF level were randomly divided into two groups namely, the control group (25), model group (80). With intraperitoneal injection of saline control group, model group were treated with intraperitoneal injection of lithium chloride solution (127mg/kg) and pilocarpine (30mg/kg). The successful established 50 epileptic rats were randomly divided into two groups, namely, irradiation group (25), non-irradiation group (25). The control group, irradiated and non-irradiated group were individually randomly divided into five different groups, namely,1 day after Gamma Knife irradiation group,1-week group, 2 weeks,4 weeks group,8-week group, each group 5.After the success of modeling, observing a period of time, when repeated seizures occur, under anesthesia the irradiated rats were fixed in location-specific gamma knife rack, Coronal magnetic resonance imaging of brain continuous scanning to determine the radiation target volume (left hippocampus) of three-dimensional coordinates. Then carry out the gamma knife irradiation scheme, using 4 mm collimator, peripheral dose of 20 Gy, and so dose curve 80%, the center dose of 25Gy.At the corresponding time points (gamma knife irradiation 1 day,1 week,2 weeks,4 weeks,8 weeks), obtained hippocampus by craniotomy under anesthesia, weighing, preparation of homogenate, add the serine, methanol in succession, and respectively centrifugating about 5min with 10000 r/min, 100μL supernatant was taken into liquid chromatography to test.Model group:55 of 80 rats occurs above gradeⅣ(the Racine classification standard) seizures at modeling, after1 week occurred repeated seizures, and gradually achieve the Racine classification standardⅢand above, included in this study.2 weeks after irradiation, the degree of seizures comes down gradually toⅡ-Ⅲdegree in irradiated group; 4 weeks after irradiation, toⅠ-Ⅱdegree. In non-irradiated group, seizure has always been in gradeⅢor above.2 weeks after irradiation, the content of Glu in the hippocampus of the rats in non-irradiated group and irradiated group were higher significantly compared with control group, that of radiation group was lower significantly compared with non-irradiated group (P<0.05). Meanwhile the content of GABA in the hippocampus of the rats in non-irradiated group and irradiated group were lower significantly compared with control group, that of radiation group was higher significantly compared with non-irradiated group (P<0.05).4 and 8 weeks after irradiation, the content of Glu was decreasing and the content of GABA was rising in the hippocampus of the rats irradiated group,, being significantly difference compared with the control group and non-irradiated group (P<0.05).1. We investigated the anti-epileptic effect of gamma knife irradiation using the epileptic rat model and discovered that low doses of gamma knife irradiation can reduce the degree of epileptic seizures in rats, and no rat died of serious complications because of the gamma knife irradiation, and further illustrate the safety and effectiveness of low-dose radiation for epilepsy.2. The content of Glu in the hippocampus of the rats in non-irradiated group increased significantly compared with control group. The content of Glu in the hippocampus of irradiated rats has the increasing trend started, but relatively slow;2 weeks after irradiation, that was lower significantly compared with non-irradiated group (P<0.05). The content of GABA in the hippocampus of the rats in non-irradiated group decreased significantly compared with control group. The content of GABA in the hippocampus of irradiated rats has the decreasing trend started, but relatively slow;2 weeks after irradiation, that was higher significantly compared with non-irradiated group (P<0.05). Note low-dose gamma knife irradiation in controlling seizures, it is also affect the content of Glu, GABA in hippocampus.We can conclude that low-dose gamma knife irradiation can regulate the balance of Glu and GABA in hippocampus to achieve anti-epileptic effect.