Fig. 5.

The GABA conductance evoked in Purkinje cells by activation of a patch of granule cells is composed of the concerted activity of ∼5 interneurons. A: estimated number of interneurons activated by photorelease of glutamate, which contributed to inhibition of Purkinje cells under our experimental conditions. The number of interneurons was estimated by extrapolating data from Hausser and Clark (1997), which demonstrated that a single interneuron prolongs the interspike interval (ISI) of Purkinje cells by ∼12% (see text for specifics on the method used for extrapolation). B: estimated number of interneurons activated under our experimental conditions using data from 2 published works. Vincent et al. (1992) and Pouzat and Hestrin (1997) characterized the interneuron-Purkinje cell inhibitory postsynaptic current (IPSC). The number of interneurons was approximated by the parameters of the IPSCs found in these 2 investigations (see text for specifics on the method of extrapolation).