Figure 5.

Occlusion of the effects of PGE₂ with forskolin, and block by TTX and Rp-cAMPs of the PGE₂ and forskolin induced up-regulation of Na⁺ current. A, Plot of Na⁺ current amplitude versus time recorded from 5 type-4 DRG cells. The horizontal bars indicate the duration of treatment with forskolin (10 µM), and forskolin + 10 µM PGE₂. Inset, Averaged current records acquired from the plot shown in (A) after treatment with forskolin and PGE₂, and following treatment with 50 nM TTX in the presence of forskolin and PGE₂. B, Plot of Na⁺ current versus time acquired from type-4 DRG cells recorded from with 100 µM Rp-cAMPs included in the pipette and treated with PGE₂ (n = 7, filled circles) or forskolin (n = 10, filled triangles). The horizontal bar indicates the duration of treatment with 10 µM forskolin or PGE₂. C, Bargraph summarizing the effects of PGE₂ and forskolin on Na⁺ currents evoked with TPs to −10 mV from type-4 DRG cells under various conditions; in the absence of Rp-cAMPs (PGE, n = 12, Forsk, n = 12), PGE₂ following up-regulation of Na⁺ current with forskolin (PGE after Forsk, n = 5), in the presence of Rp-cAMPs after an average of ≈ 25 sec following initiation of drug treatment (PGE + Rp (25 s), n = 7), (Forsk + Rp (25s), n = 10), and at the end of the plot (PGE + Rp (115 s), n = 7), Forsk + Rp (115 s), n = 10. * significant difference between the means indicated by each bracket, (p < 0.05, Mann Whitney U-test). In cases where a mean is compared multiple times the α-level has been adjusted using the Bonferroni adjustment for multiple comparisons. D, Example of a biphasic response of a type-4 DRG cell regarding PGE₂ induced changes in the amplitude of Na⁺ current evoked with TPs to −10 mV in the absence of Rp-cAMPs.