Fig. 4.

Synaptic signalling and AMPA/kainate receptor expression is downregulated upon differentiation of NG2 cells. (a,b) Four successive sweeps recorded in an NG2 cell (a) and in a premyelinating oligodendrocyte (b) in response to extracellular electrical stimulation of nearby axons in the presence of 25 μm APV and 10 μm bicuculline (the time point of stimulation is indicated by an asterisk). The holding potential is −80 mV. Synaptic responses in the NG2 cell appear with a brief latency following electrical stimulation, steeply increase to a sharp peak and then rapidly decay back to baseline (a). In a premyelinating oligodendrocyte, synchronous responses briefly after the stimulus are absent; however, there are individual release events appearing late after the stimulation and continuing for hundreds of milliseconds (b). Scale bars: 10 ms, 10 pA. (c,d) Histograms summarize the latency of synaptic currents recorded in three NG2 cells (150 events) and in five premyelinating oligodendrocytes (358 events). The cumulative peak amplitude was calculated for each latency by summing current amplitudes of all events falling into the same latency bin (bin width is 3.75 ms). The asterisks mark the time point of stimulation. (e,f) Whole-cell current responses of an NG2 cell (e) and a premyelinating oligodendrocyte (f) to glutamate un-caging, in the absence (left) or presence (right) of AMPA/kainate receptor antagonist CNQX (30 μm). The holding potential is −80 mV. The current amplitude is smaller in the premyelinating cells compared with NG2 cells. Pre-application of CNQX strongly reduces current response. Scale bar: 20 ms, 20 pA. (A–F) Modified with permission from Kukley et al. (2010).