In vitro expression and functional dection of one subunit （NR₁） of NMDA receptor

Objective: It was designed to execute in vitro expression and functional dection of one subunit （NR₁） of NMDA receptor and to investigate NR _1′s electrophysiology characteristics. Methods: Primitive NR₁ plasmid DNA from Nakanishi （Japan） was transformed into DH_5α and identified by enzyme Not I cut. Then large scale plasmid DNA was prepared and transcripted into RNA. The obtained RNA was microinjected into matured Xenopus oocytes （50 nl, 1 ng/nl） for receptor expression over 24 h incubation in modified Bath′s solution at a temperature of -19 ℃. The functions of these expressed NR₁ subunit were detected via two electrode voltage clamp technique. Results: An inward current was induced by 10^-4 mol/L NMDA in Xenopus oocytes microinjected with the obtained RNA transcripted from NR₁ plasmid DNA. The equibrilium potential of the current was -22 mV, which is close to those of chloride ions. This current could be completely inhibited by the specific antagoinst DAP 5 of NMDA receptor and was dependent on glycine （10^-4 mol/L）. This current was also blocked by the presence of Mg²⁺ , which was inhibited by the replacement of CaCl₂ with MgCl₂ in Ringer′s solution. Conclusion: The NR₁ subunit of NMDA receptor is functionally in vitro expressed in Xenopus oocytes. Its physiological and pharmacological characteristic is similar to those of whole NMDA receptor.