Global dendritic calcium spikes in mouse layer 5 low threshold spiking interneurones: implications for control of pyramidal cell bursting.
Interneuronal networks in neocortex underlie feedforward and feedback inhibition and control the temporal organization of pyramidal cell activity. We previously found that lower layer neocortical interneurones can reach action potential threshold in response to the stimulation of a single presynaptic cell. To better understand this phenomenon and the circuit roles of lower layer neocortical interneurones, we combined two-photon calcium imaging with whole cell recordings and anatomical reconstructions of low threshold spiking (LTS) interneurones from mouse neocortex. In both visual and somatosensory cortex, LTS interneurones are somatostatin-positive, concentrated in layer 5 and possess dense axonal innervation to layer 1. Due to the LTS properties, these neurones operate in burst and tonic modes. In burst mode, dendritic T-type calcium channels boosted small synaptic inputs and triggered low threshold calcium spikes, while in tonic mode, sodium-based APs evoked smaller calcium influxes. In both modes, the entire dendritic tree of LTS interneurones behaved as a 'global' single spiking unit. This, together with the fact that synaptic inputs to layer 5 LTS cells are facilitating, and that their axons target the dendritic region of the pyramidal neurones where bursts are generated, make these neurones ideally suited to detect and control burst generation of individual lower layer pyramidal neurones.
Goldberg
Jesse H
JH
Department of Biological Sciences, Columbia University, New York, NY 1002, USA. jhg24@columbia.edu
Lacefield
Clay O
CO
Yuste
Rafael
R
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D003712:Dendrites / Q000502:physiology*; D007395:Interneurons / Q000502:physiology* / Q000648:ultrastructure; D051379:Mice; D008810:Mice, Inbred C57BL; D009924:Organ Culture Techniques; D010507:Periodicity; D017966:Pyramidal Cells / Q000502:physiology*; D018091:Receptors, AMPA / Q000502:physiology; D012684:Sensory Thresholds / Q000502:physiology; D013003:Somatosensory Cortex / Q000166:cytology / Q000502:physiology; D013004:Somatostatin / Q000378:metabolism; D013569:Synapses / Q000502:physiology; D014793:Visual Cortex / Q000166:cytology / Q000502:physiology
D015220:Calcium Channels; D018091:Receptors, AMPA; D013004:Somatostatin; D002118:Calcium