| NMDA receptor (NMDAR) is one of the most important ionotropic glutamate receptor in mammal animal and human central nervous system (CNS, Central nerve system). Opening NMDAR will mediate excitatory synapses activation. After NMDAR depolarization, the intracellular calcium will be in explosive increase, downstream kinase phosphorylation signal will open access chain reaction. Therefore, NMDAR is extremely important in both physiological and pathological conditions. Under physiological conditions, when postsynaptic NMDAR activated, calcium ion passes through NMDAR from extracellular to intracellular, mediates alteration of activity-dependent long-term synaptic transmission, produces a series of electrophysiological changes, such as synaptic plasticity——long-term potentiation (LTP) and long-term depression (LTD). Currently, it is well known that NMDAR-dependent plasticity is regarded as the most important molecular mechanism of learning and memory. Under pathological conditions, excessive activation of NMDAR will lead to deficiency of ATP supply, loss of intracellular and extracellular ion concentration gradient, excess release of excitatory neurotransmitters such as glutamate, calcium overload, continously open of downstream apoptotic signaling pathways, activation of a variety of protein kinases/proteases, mitochondria necrosis, ultimately leading to neuronal degeneration, injury and/or death. NMDAR overexitation is thought to be involved in various CNS degeneration and necrosis disease (such as Alzhemer’s disease, Parkingson’s disease, Cerebral ischemia, etc.).1. Glycine exerts dual roles in pathological plasticity and cerebral ischemia through distinct mechanisms Under physiological conditions, LTP mediates long-term synaptic efficacy changes in neuronal excitability and synaptic transmission, is the basic mechanism. In pathological conditions, simulation of neurons after cerebral ischemia injury model in vitro to neurons, short time of oxygen-glucose deprivation (OGD, Oxygen and glucose deprivation) treatment can induce similar to LTP electrophysiological responses, then the classical phenomenon is named after ischemia in long-term potentiation (i-LTP post-ischemic LTP), i.e. pathology plasticity. In addition the induction process also requires NMDAR activation, but at NMDAR open extent than under physiological conditions is much higher, as an excess of open.Cerebral ischemia (Cerebral ishemia) is clinically the most common neurological diseases, stroke (Stroke) has long been the WHO definition for urgent to overcome major human diseases. Neuron protection is always the most important direction of cerebral ischemia research. Intervention neurons mediated by synaptic transmission euphoria is neuronal protection key. Many studies indicate that early ischemia can cause a short period of time various amino acids release increased, in which Gly is an important one of the increase in cash. Whether Gly is involved in the occurrence and development of downtown ischemia, have core effect was accompanied by appearance; Gly on ischemic neuronal injury is protective effect or damage, there are a lot of controversy. And the molecular mechanism by which has not previously been studied.Our laboratory of the latest research shows that, Gly may be mediated by the concentration dependence of the bidirectional plasticity. Gly at low concentrations, mainly excited NMD A receptor mediated by NMDAR-gly-site, LTP; Gly at high concentrations, mainly through the activation of the GlyR, LTD mediated by. In addition Gly mediates bidirectional plasticity of NMDAR participation. Since Gly can be received to physiological bidirectional plasticity, so come very naturally, to study whether Gly is involved in, how to participate in the pathological plasticity as well as a pathological injury after ischemia, the sense is very great. Therefore, studies of Gly involved in neuronal damage is likely to elucidate the molecular mechanisms of cerebral ischemia necrosis of the pathogenesis and clinical treatment of cerebral infarction with the necessary experimental base.The experimental part of the brain slices OGD method construction of isolated neurons after ischemia injury model, combined with the whole cell patch clamp (patch clamp) method of recording of rat hippocampal CA1pyramidal neuron excitatory postsynaptic currents (EPSC, excitatory postsynaptic currents), short time for perfusion OGD artificial cerebrospinal fluid, can be induced by i-LTP at the same time, given the different concentrations of Gly, on the i-LTP influence to judge the Gly on cerebral ischemia injury of different roles; another part is also used in the rat middle cerebral artery occlusion (MCAO, middle operation cerebral artery oclusion) in cerebral ischemia model construction method, in a simulated ischemia reperfusion after nerve injury, respectively, by intraperitoneal injection with different concentrations of Gly, observation of cerebral infarction changes to determine the Gly on cerebral ischemia in different situations.The experimental results show that, Gly on pathological plasticity has the concentration dependence of the bidirectional regulation effect. Exogenous given low concentrations of Gly can increase the amplitude of the i-LTP, and MCAO assays can further increase the ischemia and infarction area, which suggests a low concentration of Gly (L-Gly) has on ischemic neuronal damage; and given the high concentration of exogenous Gly can inhibit i-LTP, and can reduce ischemic infarction area, suggesting a high concentration of Gly (H-Gly) has on ischemic neuron protective effect. At the same time, we perfused with different concentrations of glycine transporter (GlyT) blocker, simulation of different concentrations of endogenous Gly increases, can also be observed similar two-way effect phenomenon. We further found, L-Gly damage effect is achieved by combining NMDAR-gly-site; and H-Gly protection is activated via the GlyR, and then adjusting the NMDAR subunit composition to achieve. In addition, we used in vivo microdialysis (Microdialysis) combined with MCAO experiment, accurate analysis of the cerebral ischemia before and after exogenous Gly in hippocampal area Gly concentration change.These results indicated that Gly in high concentration on cerebral ischemia has a protective effect, the GlyR is likely to become a clinical stroke research provide new therapeutic targets.2. Glycine exerts dual roles in synaptic plasticity and spatial memory through distinct mechanismsLearning and memory is always the neurobiology and even the whole human physiology research priority. Long term memory is the core problem of the study of learning and memory. Long term spatial memory (Spatial memory) and other types of long-term memory, can be divided into gain (Acquisition or Encoding),(Consolidation) and consolidate the extraction (Retrieve or Recall) in three stages.Synaptic plasticity (LTP/LTD) is considered to be the most important learning and molecular mechanisms of memory. A large body of literature that suggests, LTP/LTD and spatial memory is closely related to. In recent years on synaptic plasticity in the complexity of considerable progress, use a variety of modern biology technology, people have found that, in addition to the classic in hippocampal CA1 area of pyramidal cells using electrical stimulation can induce plasticity, but also through chemical give induced by various agents, such as small dose of Gly, D-serine and so on, can be induced by LTP; and LTD induction mechanism is more complex, in addition to ionotropic NMDAR dependence of the LTD, metabotropic glutamate receptors can also be independent participation in the LTD induced by. In addition, in your brain hippocampus than the various regions, such as the cortex, hypothalamus, cerebellum can induce LTP/LTD; besides the physiological conditions of the LTP/LTD, people also gradually found a variety of pathologic LTP/LTD. Therefore, plasticity and learning and memory between and mechanism research, has been a considerable shortage.Pharmacological and genetic evidence reveals hippocampal activity of NMDAR and NMDAR dependent synaptic plasticity (LTP/LTD) in animal spatial memory acquisition, consolidation and retrieval stage plays a key role in memory, the obtained before and memory consolidation and retrieval phases blocking the action of NMDAR, or knockout core NMDAR Asia genes (such as NR1, NR2A, NR2B), will hinder the animal long-term spatial memory formation. But the NMDAR in different forms of plasticity in the specific role of the lack of in-depth study. Discussion on NMDAR in different stages of spatial memory function, helps not only to understand the spatial memory formation process and the molecular mechanisms, may also explain the nature of memory and other problems have important enlightenment effect.Glycine (Gly) is a major inhibitory neurotransmitter in the central nervous system, with wide distribution, the neural signal transmission and participate in a variety of physiological and pathological phenomena plays an important role in. Our laboratory of the latest research shows that, Gly may be mediated by the concentration dependence of the bidirectional plasticity, and the plasticity is NMDAR dependent. Gly at low concentrations, mainly excited NMDAR-gly-site, mediated by LTP; Gly at high concentrations, mainly through the activation of the GlyR, LTD mediated by. Gly is how to participate in the hippocampal spatial memory and memory consolidation and retrieval function, and NMDAR is how to play this Gly dependence in the process of learning and memory, almost no research. So the study on Gly mediates bidirectional plasticity can affect learning and memory, it is very urgent and key issues.This experiment used, used in vivo behavior method (Morris water maze) combined with in vitro electrophysiological whole-cell patch-clamp methods recorded from CA1pyramidal neurons were observed by EPSC, Gly mediates spatial memory behavioral phenotype and electrophysiological aspects of plasticity.The experimental results show that, Gly in mediating the concentration dependence of the bidirectional plasticity. Exogenous given low concentrations of Gly can be mediated by LTP, and in vivo experimental tips on spatial memory and memory consolidation and extraction has the enhancement function; and to give high concentration of Gly can be mediated by LTD, and in vivo experimental tips on spatial memory and memory consolidation and extraction with the damage effect. High concentration of Gly mediated by LTD, reduce the spatial memory and memory consolidation is extracted from the behavioral phenotype, both for GlyR depends on.In short, Gly on rat hippocampus dependent spatial memory has a dual role, i.e., high concentration and low concentration was impaired memory, memory enhancement. GlyR is likely to become a clinical intervention on learning and memory function of new target. |
PDF Full Text Request