title: Changes in synaptic plasticity and expression of glutamate receptor subunits in the CA1 and CA3 areas of the hippocampus after transient global ischemia.
abstract: Excess glutamate release from the presynaptic membrane has been thought to be the major cause of ischemic neuronal death. Although both CA1 and CA3 pyramidal neurons receive presynaptic glutamate input, transient cerebral ischemia induces CA1 neurons to die while CA3 neurons remain relatively intact. This suggests that changes in the properties of pyramidal cells may be the main cause related to ischemic neuronal death. Our previous studies have shown that the densities of dendritic spines and asymmetric synapses in the CA1 area are increased at 12h and 24h after ischemia. In the present study, we investigated changes in synaptic structures in the CA3 area and compared the expression of glutamate receptors in the CA1 and CA3 hippocampal regions of rats after ischemia. Our results demonstrated that the NR2B/NR2A ratio became larger after ischemia although the expression of both the NR2B subunit (activation of apoptotic pathway) and NR2A subunit (activation of survival pathway) decreased in the CA1 area from 6h to 48h after reperfusion. Furthermore, expression of the GluR2 subunit (calcium impermeable) of the AMPA receptor class significantly decreased while the GluR1 subunit (calcium permeable) remained unchanged at the same examined reperfusion times, which subsequently caused an increase in the GluR1/GluR2 ratio. Despite these notable differences in subunit expression, there were no obvious changes in the density of synapses or expression of NMDAR and AMPAR subunits in the CA3 area after ischemia. These results suggest that delayed CA1 neuronal death may be related to the dramatic fluctuation in the synaptic structure and relative upregulation of NR2B and GluR1 subunits induced by transient global ischemia.
authors.affiliation: GHM Institute of CNS Regeneration (GHMICR), Jinan University, Guangzhou, Guangdong 510632, China; Department of Anatomy, Jinan University School of Medicine, Guangzhou, Guangdong 510632, China.
authors.forename: Xin-Jia
authors.initials: XJ
authors.lastname: Han
authors.affiliation: GHM Institute of CNS Regeneration (GHMICR), Jinan University, Guangzhou, Guangdong 510632, China; Department of Anatomy, Jinan University School of Medicine, Guangzhou, Guangdong 510632, China.
authors.forename: Zhong-Shan
authors.initials: ZS
authors.lastname: Shi
authors.affiliation: GHM Institute of CNS Regeneration (GHMICR), Jinan University, Guangzhou, Guangdong 510632, China.
authors.forename: Luo-Xing
authors.initials: LX
authors.lastname: Xia
authors.affiliation: GHM Institute of CNS Regeneration (GHMICR), Jinan University, Guangzhou, Guangdong 510632, China.
authors.forename: Li-Hui
authors.initials: LH
authors.lastname: Zhu
authors.affiliation: GHM Institute of CNS Regeneration (GHMICR), Jinan University, Guangzhou, Guangdong 510632, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Zeng
authors.affiliation: GHM Institute of CNS Regeneration (GHMICR), Jinan University, Guangzhou, Guangdong 510632, China.
authors.forename: Jun-Hua
authors.initials: JH
authors.lastname: Nie
authors.affiliation: Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
authors.forename: Zao-Cheng
authors.initials: ZC
authors.lastname: Xu
authors.affiliation: GHM Institute of CNS Regeneration (GHMICR), Jinan University, Guangzhou, Guangdong 510632, China; Department of Anatomy, Jinan University School of Medicine, Guangzhou, Guangdong 510632, China; Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu 226019, China; GHM Collaboration and Innovation Center for Tissue Regeneration and Repair, Jinan University, Guangzhou, Guangdong 510623, China; Ministry of Education CNS Regeneration International Collaborative Laboratory, Jinan University, Guangzhou, Guangdong 510623, China. Electronic address: tyiwen@jnu.edu.cn.
authors.forename: Yi-Wen
authors.initials: YW
authors.lastname: Ruan
mesh_terms: D000818:Animals; D056547:CA1 Region, Hippocampal / Q000378:metabolism*; D056654:CA3 Region, Hippocampal / Q000378:metabolism*; D016923:Cell Death / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism; D002546:Ischemic Attack, Transient / Q000378:metabolism*; D008297:Male; D009473:Neuronal Plasticity / Q000502:physiology*; D017208:Rats, Wistar; D018091:Receptors, AMPA / Q000378:metabolism; D017470:Receptors, Glutamate / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D013569:Synapses / Q000378:metabolism*
chemical_list: D018091:Receptors, AMPA; D017470:Receptors, Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid
keywords: glutamate receptor; hippocampus; protein expression; synapse; transient global ischemia; ultrastructure