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. 1999 Feb 1;19(3):974–986. doi: 10.1523/JNEUROSCI.19-03-00974.1999

Fig. 1.

Fig. 1.

A, Phorbol-induced potentiation of homomeric NR1 receptor currents expressed in Xenopusoocytes. Cells expressing NR1-000 variants were clamped at −80 mV in calcium replacement solutions (COS), and currents were elicited using an ∼20 sec application of agonist (100 μm NMDA, 100 μm glycine) followed by agonist wash-out. After a stable baseline (Pre-PDBu) was attained, the oocytes were incubated for 8 min in the PKC-activating agent phorbol ester dibutyrate (PDBu; 20 nm). The current trace demonstrating the peak level of potentiation induced by PDBu treatment is shown (Post-PDBu). B, When recording in the presence of calcium (COS), NR1 splice variants that do not contain the C1 exon (NR1-X0X) yield a significantly higher degree of current potentiation by PDBu compared with those variants that do contain C1 (NR1-X1X). Xenopus oocytes from a particular frog were injected with in vitro-transcribed RNA for each of the eight splice variants and were allowed to express 2–7 d in culture before recording. Currents were elicited as described inA. All currents were measured 20 sec after the initiation of the inward current. The bars represent the degree of current potentiation that each splice variant exhibited after phorbol treatment. For the results here and throughout, the degree of current potentiation is always expressed as a percentage increase from a stabilized baseline current (discussed in Materials and Methods) established before incubation in the PKC-activating agent phorbol ester dibutyrate (PDBu; 20 nm, 8 min). The nomenclature shown on the x-axis is adopted from Durand et al. (1993) and identifies the particular splice variant with the plotted data.0 or 1 indicates, respectively, the absence or presence of the alternatively spliced exons in the 5′–3′ order N1, C1, C2. Splice variants that only differ in their exon composition by the presence or absence of C1 are plotted adjacent to each other in the figure. Pairwise comparisons made between such variants demonstrate a significant difference, with C1 presence always giving rise to a lower degree of potentiation (*p < 0.001, Student’s ttest).