Abstract
Synchronized neuronal activity plays an important role in cortical information processing. The synchrony of spiking in pyramidal and non-pyramidal cells may be caused by synchronous excitatory synaptic inputs. We previously demonstrated that GABAB receptor-mediated IPSPs evoked by stimulation of layer II spread vertically throughout all layers in a columnar pattern, but not horizontally. Our study also indicates that paired pulse depression of excitatory synaptic currents is mediated by the activity of GABAB receptors. Then, it can be assumed that GABAB receptor-mediated presynaptic inhibition is suitable for modulating the coherent activity of excitatory synaptic inputs in each column. To test the hypothesis, we have performed dual whole-cell patch clamp recording in slice preparations of the barrel cortex of rats and GAD67-GFP knock-in mice. By stimulation of layers II/III, EPSCs were evoked in a pair of pyramidal or non-pyramidal cells located in neighboring two columns. Paired pulse depression of evoked EPSCs (inter-stimulus interval = 200 ms) were observed in one pyramidal or non-pyramidal cell located in the same column as the stimulating electrode was placed, but not in the other cell located in the adjacent column. Correlation coefficient was calculated between the first EPSCs and between the second EPSCs evoked in the proximal and distal cells. Coherent activity of excitatory synaptic inputs was modulated independently in each column by the activity of GABAB receptors. [Jpn J Physiol 54 Suppl:S49 (2004)]
