Figure 5.

Blockade of PKA activity with external application of H89 (8–20 μm) enhances coupling and prevents forskolin-induced modulation. A, Exposure of slices to the PKA antagonist H89 increases the estimated G_j and the cc (n = 14 bidirectional connections). Summary graphs of normalized G_j, normalized cc (n = 14 connections), and normalized R_input (n = 14 neurons; actual values were 168 ± 21 MΩ in control and 153 ± 19 MΩ) are shown on the left, whereas actual values are illustrated in the right summary graphs (Ctrl, control). Error bars are SEM. The top insets show averaged traces from a recorded pair in control and after exposure to H89 (V₁, current-injected neuron expressed in millivolts; V₂, noninjected neuron, expressed as percentage of steady-state response in V₁). B, Same organization of the figure as in A. All coupling data are averages from n = 8 bidirectional connections. R_input was 102 ± 8 MΩ in H89 versus 86 ± 9 MΩ in H89 plus forskolin (n = 8 neurons). Notice that, in the constant presence of H89, forskolin-induced modulation (50 μm) is prevented (H89, H89; H89+Frsk, H89 plus forskolin).