Figure 1.

Example single-cell stimulation pairing experiment. A, Diagram depicting the multiple patch-clamp configuration. Up to four adjacent cells were patched within the boundaries of L4. B, Top, Pairing protocol. A single presynaptic AP was elicited 10 ms after the onset of a depolarizing pulse that led to a postsynaptic burst of six to nine APs; the pairing was repeated 60 times at 0.1 Hz. Bottom, Averaged prepairing (black) and postpairing (red) traces from an example experiment. In this particular example, the unitary EPSC in response to the first action potential depressed from an average peak amplitude strength of 4.47 ± 5.07 to 2.42 ± 3.1 pA (the averaged response includes all trials, including when failures of transmission occurred; p < 0.01, Wilcoxon's test). C, Example traces of prepairing individual sequential trials of uEPSCs recorded from the postsynaptic cell in response to paired action potential stimulation of the presynaptic cell; 30 consecutive individual trials (top) and the averaged response for all 120 recorded traces (middle) are aligned to the first presynaptic action potential peak (bottom). D, Same as C, for the postpairing condition. The averaged response for 280 postpairing traces is shown as a red trace (middle). E, PDFs for the prepairing (black trace) and postpairing (red trace) conditions. F, Model fits for the prepairing (black trace) and postpairing (red trace) conditions. This connection was optimally fit by a quantal model in both conditions (prepairing number of release sites, N = 3 and quantal size, Q = 4.91 pA; postpairing, N = 2, Q = 3.6 pA). G, Time plot of peak amplitudes for all recorded trials for the connection. Horizontal gray lines indicate the average uEPSC peak amplitude before and after pairing. Horizontal dotted line indicates the 0 pA level. Synaptic failures are shown as open circles, and successful synaptic transmission events are shown as filled circles. Pairing epoch is shown as a 10 min gap.