Figure 2. Differential modulation of glutamateric synaptic plasticity of adult-born dentate granule cells by GABA.
LTP recorded from GFP+ adult-born dentate granule cells in acute slices prepared at 4 weeks (A) or 8 weeks (B) after retrovirus-mediated birth-dating and expression of GFP as in Ge et al. (2007b). Evoked postsynaptic potentials (EPSPs) were recorded from GFP+ dentate granule cells under the whole-cell current-clamp at 32–34°C and LTP was induced with a physiologically relevant theta burst stimulation (TBS) protocol consisting of four repeated episodes (at 0.1 Hz) of 10 stimuli at 100 Hz, repeated 10 times at 5 Hz and paired with a 100 pA postsynaptic current injection (as in Ge et al. 2007b). Based on the intracellular/extracellular solutions for cells recorded at both time points ([Cl−]i= 19 mm; [Cl−]o= 134.1 mm), the expected chloride reversal potential is −51 mV. Shown in the top row is an example of LTP of EPSPs recorded under the whole-cell current-clamp. Representative EPSPs averaged from five consecutive stimuli were taken before and after LTP induction by a physiologically relevant TBS (arrow) at the time points (1 and 2) indicated in the graph. Scale bars: 5 mV and 50 ms. Shown at the bottom are the summaries of LTP recorded in the presence or absence of bicuculline (10 μm) in the recording bath (artificial cerebrospinal fluid; ACSF). Normalized EPSP amplitudes are shown. Values represent means ±s.e.m. The summary plot for neurons recorded in the presence of bicucculline was adapted from Ge et al. (2007b).