Differing from other subtypes of inhibitory interneuron,chandelier or axo-axonic cells form depolarizing GABAergic synapses exclusively onto the axon initial segment(AIS)of targeted pyramidal cells(PCs).However,the de...Differing from other subtypes of inhibitory interneuron,chandelier or axo-axonic cells form depolarizing GABAergic synapses exclusively onto the axon initial segment(AIS)of targeted pyramidal cells(PCs).However,the debate whether these AIS-GABAergic inputs produce excitation or inhibition in neuronal processing is not resolved.Using realistic NEURON modeling and electrophysiological recording of cortical layer-5 PCs,we quantitatively demonstrate that the onset-timing of AIS-GABAergic input,relative to dendritic excitatory glutamatergic inputs,determines its bi-directional regulation of the efficacy of synaptic integration and spike generation in a PC.More specifically,AIS-GABAergic inputs promote the boosting effect of voltage-activated Na+channels on summed synaptic excitation when they precede glutamatergic inputs by>15 ms,while for nearly concurrent excitatory inputs,they primarily produce a shunting inhibition at the AIS.Thus,our findings offer an integrative mechanism by which AIS-targeting interneurons exert sophisticated regulation of the input-output function in targeted PCs.展开更多
基金supported by the National Natural Science Foundation of China(32130043 and 32071025)the Interdisciplinary Research Fund of Beijing Normal University,China.
文摘Differing from other subtypes of inhibitory interneuron,chandelier or axo-axonic cells form depolarizing GABAergic synapses exclusively onto the axon initial segment(AIS)of targeted pyramidal cells(PCs).However,the debate whether these AIS-GABAergic inputs produce excitation or inhibition in neuronal processing is not resolved.Using realistic NEURON modeling and electrophysiological recording of cortical layer-5 PCs,we quantitatively demonstrate that the onset-timing of AIS-GABAergic input,relative to dendritic excitatory glutamatergic inputs,determines its bi-directional regulation of the efficacy of synaptic integration and spike generation in a PC.More specifically,AIS-GABAergic inputs promote the boosting effect of voltage-activated Na+channels on summed synaptic excitation when they precede glutamatergic inputs by>15 ms,while for nearly concurrent excitatory inputs,they primarily produce a shunting inhibition at the AIS.Thus,our findings offer an integrative mechanism by which AIS-targeting interneurons exert sophisticated regulation of the input-output function in targeted PCs.
