Fig. 5.

Splice variants show a higher degree of current potentiation when coexpressed with NR2B subunits compared with NR2A subunits as a result of a reduced C1-block effect. Each of the splice variants was coinjected in a 1:10 molar ratio with either NR2A or NR2B subunits using oocytes from the same batches. To allow for the best comparison between experiments performed in COS (A) and BOS (B), a particular splice variant was recorded in both solutions within a 2 hr time frame. The data were collected from seven cells for NR2A (gray bars) and eight cells for NR2B (black bars) using three different frogs in each case. The height of the bar indicates the amount of current potentiation observed after an 8 min exposure to 20 μm PDBu. The degree of potentiation was derived by normalizing currents recorded after phorbol treatment to the baseline current recorded before treatment. The asterisks indicate variants that show a significant difference in terms of their potentiation when coexpressed with NR2B compared with NR2A subunits (Student’s ttest). A comparison between the data in A andB demonstrates that except for NR2A/NR1-000 and NR2B/010, the heteromers show no significant difference in the degree of potentiation in COS compared with BOS (Student’st test).