Fig. 3.
SOM and NOS interneurons mediate dendritic inhibition via α5-GABAARs. a Experimental design. Optogenetically targeted projections from local interneurons and the respective fields of illumination. b Light-evoked IPSCs from different interneuron populations (NOS, yellow; SOM, green; PV, red) were recorded at –70 mV in the presence of 10 µM NBQX and 25 µM AP5 using a CsCl-based pipette solution. Representative mean IPSCs before and after addition of the α5-NAM RO4938581 (1 µM, blue) show that IPSCs evoked in dendrite-targeting interneurons (NOS and SOM) were reduced. c Group means of the normalized IPSC amplitude showed a significant reduction of NOS (P < 0.001; paired t test, n = 8) and SOM-mediated IPSCs (P < 0.01; n = 7) after the addition of RO4938581, while PV-mediated IPSCs were not affected (P = 0.57, n = 8; paired t test). In addition, the effect of the α5-IA L-655,708 (50 nM) on the amplitude of SOM (P < 0.01, n = 6) and NOS IPSCs is shown (P = 0.07, n = 7). d The mean normalized PSC integral was reduced after the application of both α5-GABAR modulators for inputs from NOS and SOM interneurons (all: P < 0.05; paired t test, n = 8), while PV synapses were not affected (P = 0.08, n = 8; paired t test). e Schematic of ChR2-assisted input mapping. f Responses to stimulation of dendritic (200–300 µm from soma, top) and somatic inputs (bottom) before and after addition (blue) of the α5-NAM. g, h Group means show a significant reduction in PSC amplitude and integral for dendritic inputs (P < 0.05; paired t test, n = 8), but not for perisomatic synapses (P > 0.6; n = 8). Recording temperature T ≈ 22 °C