mRNA from NCB-20 cells encodes the N-methyl-D-aspartate/phencyclidine receptor: A Xenopus oocyte expression study

The mouse neuroblastoma-Chinese hamster brain hybrid cell line NCB-20 is the only clonal cell line in which binding studies indicate the presence of phencyclidine (PCP) receptors. We report that Xenopus oocytes injected with NCB-20 cell poly(A)⁺ RNA express N-methyl-D-aspartate (NMDA)-activated channels and that these channels include the PCP receptor site. In injected oocytes, NMDA application evoked a partially desensitizing inward current that was potentiated by glycine, blocked by the competitive antagonist D-2-amino-5-phosphonovaleric acid, blocked by Mg²⁺ and by Zn²⁺, and blocked in a use-dependent manner by the PCP receptor ligands PCP and MK-801. There was little or no response to kainate or quisqualate (agonists of the other excitatory amino acid receptors), to γ-aminobutyric acid (an inhibitory transmitter), or to glycine (an inhibitory transmitter as well as an allosteric potentiator of NMDA channels). Thus, NMDA/PCP receptors expressed from NCB-20 cell mRNA exhibit properties similar to those of the neuronal receptors. The absence of expression of other excitatory amino acid receptors in this system makes it particularly useful for study of NMDA-evoked responses without interference from responses mediated by other receptors. Moreover, NCB-20 mRNA may be an appropriate starting material for cloning the cDNA(s) encoding the NMDA/PCP-receptor complex.