Figure 3. Synaptic requirements for LTD of large-amplitude responses.

A, graph comparing the peak amplitudes of EPSPs recorded in current clamp, elicited at a fixed stimulus intensity against the corresponding EPSCs recorded in voltage clamp, over the range 300 to 1300 pA. Each point represents data from a different Purkinje cell. Linear regression was applied to produce a line of best fit (r = 0.83). EPSCs with amplitudes greater than 800 pA produced EPSPs with amplitudes greater than 9 mV (indicated by the dotted line). B, when baseline PF₁ and PF₂ EPSC amplitudes exceeded 800 pA, stimulation of PF₁ alone for 5 min at 1 Hz (horizontal filled bar) produced LTD of both PF₁ (•) and PF₂ (○) responses in six out of seven recordings. C, summary of the synaptic requirements for LTD of large-amplitude EPSCs. The bar chart shows the amplitude of PF₁ (▪) and PF₂ (□) responses 30 min after one of several different stimulus protocols; from left to right, these were PF₁ and PF₂ stimulation alone at 0.2 Hz (n = 7), 1 Hz stimulation of PF₁ alone (n = 6), 1 Hz stimulation of PF₁ combined with cell hyperpolarisation (n = 6), 1 Hz depolarisation alone (n = 6), 1 Hz PF₁ stimulation paired with depolarisation (n = 7), and 1 Hz PF₁ stimulation paired with depolarisation in the presence of 10 mm BAPTA in the patch pipette (n = 6). Asterisks indicate where a significant difference was apparent compared to the effect of 0.2 Hz stimulation alone (P < 0.05, Mann-Whitney U test, 1-tailed). Data are expressed as in Fig. 1A.