Synaptic contacts of vesicular glutamate transporter 2 fibres on chemically identified neurons of the hypothalamic suprachiasmatic nucleus of the rat

Eur J Neurosci. 2008 Nov;28(9):1760-74. doi: 10.1111/j.1460-9568.2008.06463.x.


The hypothalamic suprachiasmatic nucleus (SCN), which plays a pivotal role in the control of circadian rhythms, consists of several neuronal subpopulations characterized by different neuroactive substances. This prominent cell group has a fairly rich glutamatergic innervation, but the cell types that are targeted by this innervation are unknown. Therefore, the purpose of the present study was to examine the relationship between the afferent glutamatergic axon terminals and the vasoactive intestinal polypeptide (VIP)-, arginine-vasopressin (AVP)- and gamma-aminobutyric acid (GABA)-positive neurons of the SCN. Glutamatergic elements were revealed via immunocytochemical double-labelling for vesicular glutamate transporter type 1 (VGluT1) and type 2 (VGluT2), and brain sections were imaged via confocal laser-scanning microscopy and electron microscopy. Numerous VGluT2-immunoreactive axons were observed to be in synaptic contact with VIP- and GABA-positive neurons, and only a few synapses were detected between VGluT2 boutons and AVP neurons. VGluT1 axon terminals exhibiting very moderate distribution in this cell group were observed to be in synaptic contact with chemically unidentified neurons. The findings provide the first morphological data on the termination of presumed glutamatergic fibres on chemically identified neurons of the rat SCN, and indicate that all three prominent cell types of the cell group receive glutamatergic afferents.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Arginine Vasopressin / metabolism
  • Glutamic Acid / metabolism*
  • Male
  • Microscopy, Confocal
  • Microscopy, Immunoelectron
  • Neurons / classification
  • Neurons / metabolism
  • Neurons / ultrastructure
  • Presynaptic Terminals / metabolism*
  • Presynaptic Terminals / ultrastructure
  • Rats
  • Rats, Wistar
  • Suprachiasmatic Nucleus / metabolism*
  • Suprachiasmatic Nucleus / ultrastructure
  • Synapses / metabolism
  • Synapses / ultrastructure
  • Synaptic Transmission / physiology*
  • Vasoactive Intestinal Peptide / metabolism
  • Vesicular Glutamate Transport Protein 1 / metabolism
  • Vesicular Glutamate Transport Protein 2 / metabolism*
  • gamma-Aminobutyric Acid / metabolism


  • Slc17a6 protein, rat
  • Slc17a7 protein, rat
  • Vesicular Glutamate Transport Protein 1
  • Vesicular Glutamate Transport Protein 2
  • Arginine Vasopressin
  • Vasoactive Intestinal Peptide
  • Glutamic Acid
  • gamma-Aminobutyric Acid