Expression of NR1, NR2A-D, and NR3 subunits of the NMDA receptor in the cerebral cortex and olfactory bulb of adult rat

Quantitative reverse transcriptase - polymerase chain reaction was used to analyze the relative expressions of NR1, NR2A, NR2B, NR2C, NR2D, and NR3 su bunits of the NMDA receptor in the piriform, entorhinal, visual, and motor cortices as well as in the olfactory bulb of adult rat. The analysis detect ed clear differences in the relative proportions of the NMDA receptor subun its between the five forebrain regions examined. These differences were par ticularly striking when the piriform and motor cortices were compared. In t he piriform cortex, NR1 was the predominant transcript. The expression of N R2A was only slightly higher than half of that of NR1. NR2B was expressed e ven at lower levels (similar to 30% of NR1). NR2C and NR3 were expressed at levels which were approximately 15% of those of NR1. NR2D had the lowest l evels of expression (similar to 3% of NR1). In contrast, NR2B was the predo minant transcript in the motor cortical region, where it was expressed at t he levels close to 135% of those of NR1 message. NR2A had the levels of exp ression of approximately 50% of those of NR1. The NR2C expression was close to 25% that of NR1, and the NR2D and NR3 transcripts were totally absent f rom this cortical area. These findings suggest a significant regional varia bility of the NMDA receptors in the adult rat forebrain. (C) 2000 Wiley-Lis s, Inc.