Figure 4.

Changes in postsynaptic receptor sensitivity parallel the LTD of PF transmission. (A) PF and caged glutamate responses before (control) and 15 min after LTD was induced (LTD); responses recorded before and after LTD are superimposed at right. Traces are averages of five PF responses or two caged glutamate responses. The uncaging spot was placed within 3 μm of the PF stimulation pipette in this experiment. (B) Time course of changes in PF responses during LTD. LTD was induced by pairing PF activity with Purkinje cell depolarization during the time indicated by the horizontal bar. Points represent mean values for peak amplitude of EPSCs measured at the indicated times and bars indicate SEM determined for six experiments. (C) Time course of LTD-induced changes in Purkinje cell responses to uncaged glutamate, from the same experiments shown in B. Points represent mean amplitudes of glutamate responses and bars indicate SEM. (D) Superimposed time courses of LTD-induced changes in responses to PF stimuli (filled symbols) and uncaged glutamate (open symbols). (E) Relationship between peak amplitudes of PF and caged glutamate responses. Open symbols indicate responses measured before pairing PF activity with depolarization, and filled symbols indicate responses measured afterward. Dashed line has a slope of 1.