Specificity of synaptic connectivity between layer 1 inhibitory interneurons and layer 2/3 pyramidal neurons in the rat neocortex

Christian Wozny, Stephen R. Williams

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83 Citations (Scopus)


Understanding the structure and function of the neocortical microcircuit requires a description of the synaptic connectivity between identified neuronal populations. Here, we investigate the electrophysiological properties of layer 1 (L1) neurons of the rat somatosensory neocortex (postnatal day 24-36) and their synaptic connectivity with supragranular pyramidal neurons. The active and passive properties of visually identified L1 neurons (n = 266) suggested division into 4 groups according to the Petilla classification scheme with characteristics of neurogliaform cells (NGFCs) (n = 72), classical-accommodating (n = 137), fast-spiking (n = 23), and burst-spiking neurons (n = 34). Anatomical reconstructions of L1 neurons supported the existence of 4 major neuronal groups. Multiparameter unsupervised cluster analysis confirmed the existence of 4 groups, revealing a high degree of similarity with the Petilla scheme. Simultaneous recordings between synaptically connected L1 neurons and L2/3 pyramidal neurons (n = 384) demonstrated neuronal class specificity in both excitatory and inhibitory connectivity and the properties of synaptic potentials. Notably, all groups of L1 neurons received monosynaptic excitatory input from L2/3 pyramidal neurons (n = 33), with the exception of NGFCs (n = 68 pairs tested). In contrast, NGFCs strongly inhibited L2/3 pyramidal neurons (n = 12 out 27 pairs tested). These data reveal a high specificity of excitatory and inhibitory connections in the superficial layers of the neocortex.
Original languageEnglish
Pages (from-to)1818-1826
Number of pages9
JournalCerebral Cortex
Issue number8
Early online date10 Jan 2011
Publication statusPublished - 1 Aug 2011


  • animals
  • cell communication
  • interneurons
  • neocortex
  • neural inhibition
  • neural pathways
  • organ culture techniques
  • pyramidal cells
  • rats
  • rats, Wistar
  • somatosensory cortex
  • synapses
  • synaptic transmission

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