Efficient recruitment of layer 2/3 interneurons by layer 4 input in single columns of rat somatosensory cortex

J Neurosci. 2008 Aug 13;28(33):8273-84. doi: 10.1523/JNEUROSCI.5701-07.2008.


Interneurons in layers 2/3 are excited by pyramidal cells within the same layer (Reyes et al., 1998; Gupta et al., 2000), but little is known about translaminar innervation of these interneurons by spiny neurons in the main cortical input layer 4 (L4). Here, we investigated (1) how efficiently L4 spiny neurons excite L2/3 interneurons via monosynaptic connections, (2) whether glutamate release from axon terminals of L4 spiny neurons depends on the identity of the postsynaptic interneuron, and (3) how L4-to-L2/3 interneuron connections compare with L4-to-L2/3 pyramidal neuron connections. We recorded from pairs of L4 spiny neurons and L2/3 interneurons in acute slices of rat barrel cortex of postnatal day 20 (P20) to P29 rats. The L4-to-L2/3 interneuron connections had an average unitary EPSP of 1.2 +/- 1.1 mV. We found an average of 2.3 +/- 0.8 contacts per connection, and the L4-to-L2/3 interneuron innervation domains were mostly column restricted. Unitary EPSP amplitudes and paired-pulse ratios in the L4-to-L2/3 interneuron connections depended on the "group" of the postsynaptic interneuron. Averaged over all L4-to-L2/3 interneuron connections, unitary EPSP amplitudes were 1.8-fold higher than in the translaminar L4-to-L2/3 pyramidal cell connections. Our results suggest that L4 spiny neurons may more efficiently recruit L2/3 interneurons than L2/3 pyramidal neurons, and that glutamate release from translaminar boutons of L4 spiny neuron axons is target cell specific.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / physiology
  • Animals
  • Interneurons / cytology*
  • Interneurons / physiology*
  • Interneurons / ultrastructure
  • Organ Culture Techniques
  • Rats
  • Rats, Wistar
  • Recruitment, Neurophysiological / physiology*
  • Somatosensory Cortex / cytology*
  • Somatosensory Cortex / physiology*
  • Somatosensory Cortex / ultrastructure
  • Synaptic Transmission / physiology