The Influence Of Gamma Knife On Expression Of The NMDA Receptor In Epilepsy Rat Cortical Neurons In Vitro

Epilepsy is a chronic recurrent episodes of transient cerebral dysfunction syndrome, the abnormal discharge characteristics of the onset of a epileptic was caused by neurons。There are about 6 million of epilepsy patients in our country, and have more than 0.4 million new cases every year. At least 1.2 million epileptic seizures patients are difficult to control by drugs, long-term recurrent become medically intractable epilepsy that serious impacted the life quality of patients with epilepsy. 30% to 40% of epilepsy patients have cognitive impairment, mainly for attention, memory, planning ability to judge the decline. It has been a heavy burden and stress both for families and society.Glutamic acid-methyl-D-aspartat (Nmethyl-D-aspartatereceptor, NMDA) receptor is a kind of special proteins of ion channel ,different subunits (N-methyl-D-aspartate receptorsubunit, NR) composed of tetramer or pentamer, sub-units belonging to three families, namely receptor NR1, NR2 and NR3.The NR2 has four independent subunit that NR2A, NR2B, NR2C and NR2D。NR3 has four independent subunits that NR3A and NR3B.NR1 is function subunit. NR2 and NR3 are the regulatory subunits. They are distributed in the cerebral cortex and other parts. They have many different allosteric regulatory sites. They were not only dominated by the synaptic voltage, but also controlled by the neurotransmitters, such as glutamate, glycin and NMDA. NMDA receptor channels are highly transparent on the ca²⁺. In normal physiological conditions, the channel is not open because of the blocking effect of mg²⁺. Many studies showed that the NMDA receptors are closely related to the epilepsy. NMDA receptor channels are highly permeable to the ca²⁺. The Mg²⁺ block the NMDA receptor channels in the normal physiological conditions. The abnormal discharge of neurons caused the cell membrane depolarization, the receptor protein conformational changed, so that the NMDA receptor was activated, ion channel opening, Ca²⁺ over-influx, causing Intracellular Ca²⁺ overload, resulting in excitotoxic nerve cell injury.NMDA receptor subunit is well controlled by the seizures, and also involved in the occurrence of seizures, development and synaptic reorganization after seizures。There are at least 1.2 million of epileptic seizures patients who can't be well controlled by drugs, long-term recurrent become medically intractable epilepsy, that serious impact the quality of life of patients. The main treatment means of these patients is surgical. The purpose of surgical is to damage the abnormal discharge pathway or resect the lesion to reduce or even stop the seizure onset. However, with the progressing of functional imaging technology, from the earliest reported in 1959 by the Talairach application of X knife treatment of epilepsy to Lindquitst first use the gamma knife treatment successfully[14], as well as the accuracy of the noninvasive positioning the lesion and the risk is lower than surgery, stereotactic radiosurgery has attracted attention. The advantage of stereotactic radiosurgery leads us to explore mechanism of Gamma Knife on treatment of epilepsy.Objective: To investigate the influence of Gamma knife of expression of NMDA receptor in epilepsy rat cortical neurons in vitro.Methods: Primary cultured cortical neurons cells of newborn rats were randomly divided into two groups: epilepsy group, gamma knife group. The neuron model of epilepsy was established by treatment cortical neurons cells with "magnesium-free" medium for 3 hs after 14 days primary cortical neurons cells cultruing, and then put it back into the normal medium with magnesium. The neuron model of epilepsy was implementation of the gamma knife irradiation with central dose of 30Gy by using stereotactic techniques in the experimental group. The protein and mRNA expression of NR1, NR2A, NR2B were detected by immunocytochemistry and RT-PCR methods after irradiation 1,3,7,10 days both in gamma knife group and control group. Results: Immunocytochemistry showed that protein expression of NMDA receptor subunits NR1, NR2A, NR2B were significantly reduced on gamma knife group compared with control group after gamma knife irradiation 3,7,10 days. Consistently with the protein expression, the gamma knife group had decreased on mRNA expressions of NR1, NR2A, NR2B comparing with control group. P <0.05, the difference was statistically significant.Conclusion: The protein and mRNA expression of NMDA receptor subunits NR1, NR2A, NR2B were significantly reduced in gamma knife irradiation with 30Gy comparing with control group. That may be one of the mechanisms of gamma knife treatment epilepsy and provide the theoretical basis of epilepsy treatment.