VGLUT1-independent transmission responds differently to repetitive stimulation. (A) Initial responses to 10-Hz repetitive stimulation overlap in postnatal day 9 to 10 in hippocampal slices from wild-type and knockout mice but begin to separate after three stimuli (*, P < 0.05; wild type/heterozygote, n = 31; VGLUT1-/-, n = 28). fEPSP slopes were measured at 0.1 Hz before the onset of stimulation and amplitudes were normalized to baseline fEPSPs. Some data points overlap and are masked. Sample traces above the graph correspond to the first five stimuli of the stimulation train in wild type/heterozygote (top) and knockout (bottom). Error bars show mean ± SEM. +/+,+/- scale bar, 0.2 mV, 5 ms. -/- scale bar, 0.1 mV, 5 ms. (B) The response to prolonged repetitive stimulation (300 pulses at 10 Hz) declines more rapidly and recovers more slowly in knock- out mice relative to that of the wild type (*, P < 0.05; wild type/heterozygote, n = 31; VGLUT1-/-, n = 28). Responses to repetitive stimulation were binned (bin size = 0.4 s) and normalized to fEPSP slopes measured before the onset of stimulation.