Electrophysiological Characterization of AMPA and NMDA Receptors in Rat Dorsal Striatum

Electrophysiological Characterization of AMPA and NMDA Receptors in Rat Dorsal Striatum

The striatum receives glutamatergic afferents from the cortex and thalamus, and these synaptic transmissions are mediated byՁ-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) and N-methyl- D-aspartate (NMDA) receptors. The purpose of this study was to characterize glutamate receptors by analyzing NMDA/AMPA ratio and rectification of AMPA and NMDA excitatory postsynaptic currents (EPSCs) using a whole-cell voltage-clamp method in the dorsal striatum. Receptor antagonists were used to isolate receptor or subunit specific EPSC, such as (DL)-2-amino-5-phosphonovaleric acid (APV), an NMDA receptor antagonist, ifenprodil, an NR2B antagonist, CNQX, an AMPA receptor antagonist and IEM-1460, a GluR2-lacking AMPA receptor blocker. AMPA and NMDA EPSCs were recorded at −70 and ＋40 mV, respectively. Rectification index was calculated by current ratio of EPSCs between ＋50 and −50 mV. NMDA/AMPA ratio was 0.20±0.05, AMPA receptor ratio of GluR2-lacking/GluR2- containing subunit was 0.26±0.05 and NMDA receptor ratio of NR2B/NR2A subunit was 0.32±0.03. The rectification index (control 2.39±0.27) was decreased in the presence of both APV and combination of APV and IEM-1460 (1.02±0.11 and 0.93±0.09, respectively). These results suggest that the major components of the striatal glutamate receptors are GluR2-containing AMPA receptors and NR2A- containing NMDA receptors. Our results may provide useful information for corticostriatal synaptic transmission and plasticity studies.