(A) A reconstruction of a SOM-IN showing soma and dendrites (black) and axon (red) with respect to the layers of the CA1 area. Inset (top left), intrinsic physiological response to current injections (500 ms duration; −250 pA to 250 pA). Inset (right), immunoreactivity for SOM (green) in the same biocytin-filled cell (bioc, blue). The arrows indicate SOM immunoreactivity in somata of the biocytin-filled (upper) and non-filled (lower) INs. Scale bar: 20 µm. (B, upper) EPSCs elicited in a SOM-IN by alveus stimulation in the presence of 10 µM bicuculline, during control (left), baclofen (10 µM, middle, control traces are overlain in red) and CGP-55,845 (CGP, 5 µM, right) bath application. (B, lower) Time-course plot of the mean EPSC amplitude in 10 SOM-INs during control, and sequential bath application of baclofen, CGP and NBQX (10 µM). (C,D) Summary bar graphs of EPSC amplitudes and PPRs under control conditions (Ctrl) and during baclofen and subsequent CGP application from 9 SOM-INs. (E) Monosynaptic IPSCs evoked by stimulation of str. oriens in the presence of NBQX and APV (50 µM, top) and time-course plot of the mean IPSC amplitude from 9 SOM-INs (bottom) during control, and sequential bath application of baclofen, CGP and bicuculline (Bic, 10 µM). (F,G) Summary bar graphs of IPSC amplitudes and PPR from 9 SOM-INs. Connected circles correspond to data obtained from a single SOM-IN in the different conditions. Statistics shown: ns – p>0.05, * – p<0.05, ** – p<0.01, *** - p<0.001; all from repeated measures ANOVA with Holm-Sidak post-tests. Abbreviations: Ori - str. oriens, Pyr - str. pyramidale, Rad - str. radiatum, L-M - str. lacunosum-moleculare, DG – dentate gyrus.