脳スライス標本における電気刺激効果範囲の検討

抄録

In order to examine the confines of electrical stimulation in layer 2/3 of visual cortex in the brain slice preperation, we estimated the effective range of the stimulation based on the excitatory postsynaptic potential (EPSP) evoked in layer V neuron which receives input from layer 2/3. For this purpose, we recorded and compared EPSPs amplitudes evoked by stimulations at directly over site of recording electrode and lateral site in layer 2/3. Since the EPSP increased linearly with stimulus intensity before the saturation, it was considered that the EPSP correlates with the number of projecting neurons in area directly excited with the stimulation. Then we formed the region model by which we can get the ratios between the neuron numbers in areas excited by different sites stimulation against the stimulus effective ranges. And in the stimulus intensity for action potential threshold of layer 5 neuron, we evaluated the effective range for the relative values of EPSPs to be produced with the stimulations of 250μm lateral site and directly over site. In the model, the ratio increased monotonically with the effective range and in the case of 250μm for the effective range, the ratio bewteen those EPSPs was less than the value in the model. These results led the conclusion that the effective range of the intensity for layer 5 neuron to generate the output is confined within 250μm from directly over site, that is, within layer 2/3.