Figure 6.

Blocking GluR2-lacking AMPARs abolishes feedforward inhibition evoked by stimulation of TC afferents. A, Top, Recording configuration. Traces: Bulk stimulation of TC afferents triggers a feedforward IPSC in an RS cell (top, voltage clamped at −65 mV; see Materials and Methods for isolation of IPSC) and an EPSC in a simultaneously recorded FS cell (bottom, voltage clamped at E_IPSC). Application of the GluR2-lacking AMPAR blocker NASPM (green) abolishes the feedforward IPSC recorded in the RS cell and decreases the EPSC recorded in the FS cell. In contrast, the EPSC evoked in the RS cell (isolated by voltage clamping the neuron at E_IPSC, inset) remains unaffected. Bottom, Summary data. B, Top, Recording configuration (I-clamp: current clamp). Traces: Bulk stimulation of TC afferents triggers an EPSP-IPSP sequence in an RS cell (top, current clamp configuration) and an EPSC in a simultaneously recorded FS cell (bottom, voltage clamped at E_IPSC). Application of NASPM (green) abolishes the feedforward IPSP recorded in the RS cell, thereby increasing the amplitude and prolonging the time course of the EPSP. As in A, NASPM decreases the EPSC recorded in the FS cell. Bottom, Summary graph of the effect of NASPM on the peak amplitude and half width of the postsynaptic potential recorded in RS cells. C, Left, Recording configuration as in A. The NMDAR antagonist CPP (25 μm, green) has no effect either on the feedforward IPSC recorded in the RS cell (top) or on the EPSC recorded in the RS cells (inset) or FS cells (bottom). Right, Summary graph.