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. 2001 Apr 1;532(Pt 1):73–90. doi: 10.1111/j.1469-7793.2001.0073g.x

Figure 8. cAMP removes the agonist-induced inhibition and potentiates the Bay K-modified L-channels.

Figure 8

A, channel activity with high Po during consecutive depolarizations to +10 mV after incubation with 1 mm 8-CPT-cAMP (30 min) and in the presence of ATP and opioid agonists in the pipette; Vh -40 mV. The mean current to the bottom was calculated from 164 sweeps pooled from 16 patches. B, with ATP and opioids in the pipette the L-channel activity was low (top): mean Po was 0.13 and the nulls (indicated by spaces) were quite frequent (26 %). Following 8-CPT-cAMP (50 μm) incubation (with agonists in the pipette) Po increased to 0.30 and the percentage of nulls was reduced to 9 %. C, open and close time distributions at +10 mV derived from n = 164 sweeps pooled from 16 patches incubated with 1 mm 8-CPT-cAMP. Data were plotted on a square root-log binned histogram and fitted with two and three exponentials with the following values: 3.9 ms (86 %) and 11.7 ms (14 %) for to and 1.64 ms (71 %), 13.6 ms (21 %) and 61 ms (8 %) for tc. D-G, mean Po, null sweeps, mean to and tc at +10 mV in the presence of the agonists (27 patches), agonists + 1 mm cAMP (16 patches), agonists + cAMP + PTX (7 patches) and cAMP + antagonists (n = 10 patches) (**P < 0.01).