Figure 3.

Pharmacological elevation of intracellular cAMP levels reduces coupling between interneurons. A, Bath application of the adenylyl cyclase stimulator forskolin (50 μm) reduces the estimated G_j and the cc. Summary plots of the normalized G_j, cc (n = 20 bidirectional connections), and R_input (n = 20 neurons; absolute values were 139 ± 16 MΩ in control and 129 ± 15 MΩ in the presence of the drug) are shown in the left side of the figure, whereas plots of the actual values of G_j and cc (n = 20 bidirectional connections) are shown in the right (Ctrl, control; Frsk, forskolin). Error bars are SEM. Averaged traces from a coupled pair are shown in the top inset. Electrotonic responses to current injection recorded in the first cell of the pair (V₁) are shown in millivolts, whereas propagated responses to the noninjected cell (V₂) are expressed as percentage of the steady state of V₁. B, Similar experiment using the inactive analog dideoxyforskolin (50 μm) shows no effects on coupling. The organization of the plots and traces is identical with that of A (Dfrsk, dideoxyforskolin). Data from n = 20 connections and 20 neurons. Average R_input was 129 ± 11 MΩ in control versus 111 ± 9 MΩ after application of dideoxyforskolin.