Figure 8.

Tonic inhibition regulates the flow of sensory information to molecular layer interneurons. A, Schematic diagram showing recording configuration and direction of information flow through the cerebellar cortex. MF, mossy fiber; GC, granule cell; PF, parallel fiber; IN, interneuron; PC, Purkinje cell. B, Morphological identification of a molecular layer interneuron (basket cell, 254 μm from pial surface) obtained following biocytin labeling via the recording electrode and subsequent staining with streptavidin Alexa Fluor 488. ML, molecular layer; PCL, Purkinje cell layer. Scale bar, 10 μm. C, Effects of gabazine (500 μm) on spontaneous and sensory-evoked EPSC amplitudes (gray symbols, 20 consecutive traces overlaid) and frequency (yellow symbols, single representative trace) recorded at −70 mV. Insets show example current recordings in the two conditions. D, Representative PSTHs of spontaneous and sensory-evoked parallel fiber EPSCs (20 trials) in control and gabazine. Bin size = 50 ms. E, Effects of gabazine on the SNR of parallel fiber synaptic input to molecular layer interneurons (n = 4). Gabazine data were corrected for effects on Golgi cell-mediated inhibition (see Materials and Methods). F, Effects of THIP (10 μm) on spontaneous and sensory-evoked EPSC amplitudes (gray symbols, 20 consecutive traces overlaid) and frequency (yellow symbols, single representative trace) recorded at −70 mV. Insets show example current recordings in the two conditions. G, PSTHs of spontaneous and sensory-evoked parallel fiber EPSCs (20 trials) in control and THIP. Bin size = 50 ms. H, Effects of THIP on the SNR of parallel fiber synaptic input to molecular layer interneurons (n = 5).