Figure 1
Homosynaptic postburst depression and transient heterosynaptic depression result in different changes in paired-pulse ratio. A, Schematic representation of the experimental protocol for postburst depression (PBD) and transient heterosynaptic depression (tHeSD). Our standard protocol consisted of a 3-impulse, 50 Hz, burst before a paired-pulse test stimulus applied either homosynaptically (PBD, black), or heterosynaptically (tHeSD, red). B, Relationship between relative synaptic efficacy and paired-pulse ratio (PPR) measured with field recordings. Synaptic efficacy is normalized to control, which is set to 1. PPR was evaluated using an interstimulus interval of 20 ms (circles) and 50 ms (squares). Data are represented as mean ± SEM with the following number of experiments; control 50 ms (n = 28), control 20 ms (n = 28), tHeSD 50 ms (n = 29) Error bars are within the symbol. PBD 50 ms (n = 28) and PBD 20 ms (n = 28). C, Relative change of the 1st and 2nd fEPSP, as well as PPR in association with the tHeSD. Interstimulus interval 50 ms. On top are example paired-pulse recordings without (left) and with (right) preceding heterosynaptic conditioning, calibration bar 20 ms, 100 μV. D, Relative change of the 1st and 2nd fEPSP, as well as PPR in association with the PBD. Interstimulus interval 20 ms. The top inset show example traces from the conditioning three-impulse burst and the test paired-pulse stimulation, calibration bar 20 ms, 100 μV.