Presynaptic effect of chondroitin sulfate. (a) Time-course of averaged facilitation of fEPSP evoked by paired pulses at 50 ms intervals and applied every 15 s. Note the facilitation exerted by CS (300 μM) applied during the time indicated by the top horizontal bar. (b) Representative fEPSPs recorded in response to paired stimuli separated by 50 interpulse intervals in control A and after 20 min of CS (300 μM) application B. The amplitudes evoked correspond to the 40–50% of maximal response. Data are mean ± SEM of 14 slices evaluated.