Electrophysiological characterization of synaptic connections between layer VI cortical cells and neurons of the nucleus reticularis thalami in juvenile rats

Eur J Neurosci. 2004 Feb;19(3):625-33. doi: 10.1111/j.1460-9568.2004.03168.x.


Corticothalamic (CT) feedback projections to the thalamus outnumber sensory inputs from the periphery by orders of magnitude. However, their functional role remains elusive. CT projections may directly excite thalamic relay cells or indirectly inhibit them via excitation of the nucleus reticularis thalami (nRT), a nuclear formation composed entirely of gamma-aminobutyric acidergic neurons. The relative strengths of these two pathways will ultimately control the effects of CT projections on the output of thalamic relay cells. However, corticoreticular synapses have not yet been fully physiologically characterized. Here, local stimulation of layer VI cells by focal application of K+ or AMPA elicited excitatory postsynaptic potentials in nRT neurons with a mean peak amplitude of 2.4 +/- 0.1 mV (n = 75, mean +/- SEM), a mean rise time (10-90%) of 0.74 +/- 0.03 ms and a weighted decay time constant of 11 +/- 0.3 ms. A pharmacological profile of responses was drawn in both current-clamp and voltage-clamp modes, showing the presence of a small N-methyl-d-aspartate receptor-dependent component at depolarized potentials. In two pairs of synaptically coupled layer VI cell-nRT neuron, moderate rates of transmission failures were observed while the latencies were above 5 ms in both cases. Our results indicate that the corticoreticular pathway fulfills the criteria for 'modulatory' inputs and is temporally restricted. We suggest that it may be involved in coincidence detection of convergent corticoreticular signals.

Publication types

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

MeSH terms

  • Animals
  • Animals, Newborn
  • Cerebral Cortex / cytology*
  • Cerebral Cortex / physiology
  • Drug Interactions
  • Electric Stimulation
  • Excitatory Amino Acid Agonists / pharmacology
  • Excitatory Amino Acid Antagonists / pharmacology
  • Excitatory Postsynaptic Potentials / drug effects
  • Excitatory Postsynaptic Potentials / physiology
  • GABA Antagonists / pharmacology
  • In Vitro Techniques
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Neural Conduction / drug effects
  • Neural Inhibition / drug effects
  • Neural Inhibition / physiology
  • Neurons / drug effects
  • Neurons / physiology*
  • Patch-Clamp Techniques
  • Picrotoxin / pharmacology
  • Potassium / pharmacology
  • Quinoxalines / pharmacology
  • Rats
  • Rats, Wistar
  • Synapses / drug effects
  • Synapses / physiology*
  • Thalamic Nuclei / cytology*
  • Thalamic Nuclei / drug effects
  • Thalamic Nuclei / physiology
  • Valine / analogs & derivatives*
  • Valine / pharmacology
  • alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / pharmacology


  • Excitatory Amino Acid Agonists
  • Excitatory Amino Acid Antagonists
  • GABA Antagonists
  • Quinoxalines
  • Picrotoxin
  • FG 9041
  • 2-amino-5-phosphopentanoic acid
  • alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid
  • Valine
  • Potassium