Figure 2.

PDBu stimulates SERCA-mediated recovery from action potential-induced increases in [Ca²⁺]_i. [Ca²⁺]_i was recorded from single rat DRG neurons using indo-1-based photometry. A–D, DRG neurons were cotransfected with plasmids containing an EGFP reporter construct and an antisense PMCA4 cDNA (AS4). Recordings are from EGFP-positive cells. A, Brief trains of action potentials (3–5s, 6–10 Hz) were delivered every 4 min to an AS4-expressing cell as indicated by the filled triangles. PDBu at 0.5 μm was applied to the bath during the time indicated by the horizontal bar. B, Representative [Ca²⁺]_i responses in the absence and presence of PDBu, indicated by arrows in A, were superimposed on an expanded timescale. C, Rate constants describing the recovery kinetics for individual responses from experiments such as the one shown in A were normalized to the first response and plotted versus time. PDBu was applied after the fourth stimulus. Experiments were performed in the absence (open circles; n = 5) and presence (filled circles; n = 11) of 5 μm CPA applied 30 min before beginning the recording. Data points are means ± SEM. *p < 0.05 relative to the same time point when CPA was not added, one-way ANOVA with Bonferroni's post hoc test. Results in the presence of CPA are replotted from Usachev et al. (2002). D, Bar graph summarizes results of various combinations of SERCA and PMCA4 block on the PDBu effect. *p < 0.05, relative to untreated control (no AS4 and no CPA); ^#p < 0.05 relative to cells expressing AS4 (no CPA); Student's t test.