Figure 6.

Intracellular blockade of PKA activity with KT5720-loaded electrodes (1 μm) prevents forskolin-induced (50 μm) modulation of coupling. A, After 10 min of forskolin application in a connected pair of neurons recorded with standard electrodes, repatching one cell of the pair with a KT5720-loaded pipette blocks forskolin-induced modulation of coupling. Summary graphs of normalized G_j, normalized cc, and normalized R_input (132 ± 9 MΩ in control vs 123 ± 9 MΩ after repatching with KT5720-loaded electrodes) are shown in the left for n = 16 bidirectional connections and n = 16 neurons, whereas actual values are illustrated in the right summary graphs (Ctrl, control; Frsk+KT, forskolin plus intracellular KT5720). Error bars are SEM. The dotted and solid lines represent the experimental results of Figure 3 for reference (dotted line, normalized G_j; solid line, normalized cc). The top insets show averaged traces from a recorded pair in control and after one cell of the pair was repatched with pipettes containing the PKA inhibitor (V₁, current-injected neuron; V₂, noninjected neuron). B, Same organization of the figure as in A. However, repatching was performed with a control pipette lacking the PKA inhibitor. Notice that repatching in the absence of KT5720 does not impair forskolin-induced modulation (Frsk+KT, forskolin plus KT5720). Shown are summary data from n = 18 bidirectional connections and n = 18 cells. R_input was 123 ± 8 MΩ in control versus 122 ± 6 MΩ after repatching with control electrodes (n = 18 neurons).