Variable Dendritic Integration in Hippocampal CA3 Pyramidal Neurons

• Published in: Neuron (Cambridge, Mass.) Vol. 80; no. 6; pp. 1438 - 1450
• Main Authors: Makara, Judit K., Magee, Jeffrey C.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 18.12.2013; Elsevier Limited; Cell Press
• Subjects: Action Potentials - physiology; Animals; Brain; CA3 Region, Hippocampal - physiology; Dendrites - physiology; Experiments; G Protein-Coupled Inwardly-Rectifying Potassium Channels - physiology; Glutamic Acid - pharmacology; Male; N-Methylaspartate - physiology; Neurons; Potassium Channels; Pyramidal Cells - physiology; Rats; Sodium - physiology
• ISSN: 0896-6273; 1097-4199
• DOI: 10.1016/j.neuron.2013.10.033

The hippocampal CA3 region is essential for pattern completion and generation of sharp-wave ripples. During these operations, coordinated activation of ensembles of CA3 pyramidal neurons produces spatiotemporally structured input patterns arriving onto dendrites of recurrently connected CA3 neurons. To understand how such input patterns are translated into specific output patterns, we characterized dendritic integration in CA3 pyramidal cells using two-photon imaging and glutamate uncaging. We found that thin dendrites of CA3 pyramidal neurons integrate synchronous synaptic input in a highly supralinear fashion. The amplification was primarily mediated by NMDA receptor activation and was present over a relatively broad range of spatiotemporal input patterns. The decay of voltage responses, temporal summation, and action potential output was regulated in a compartmentalized fashion mainly by a G-protein-activated inwardly rectifying K+ current. Our results suggest that plastic dendritic integrative mechanisms may support ensemble behavior in pyramidal neurons of the hippocampal circuitry. •Active nonlinear dendritic integration in CA3 pyramidal neurons•NMDARs mediate amplification of synchronous synaptic inputs•Compartmentalized control of dendritic integration and somatic output by K+ channels Makara and Magee demonstrate NMDA receptor-mediated supralinear dendritic integration of multiple coactive synaptic inputs in thin dendrites of hippocampal CA3 pyramidal neurons and reveal a powerful regulation of these NMDA spikes by G-protein-activated inwardly rectifying K+ channels.