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

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Abstract

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 γ-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.

Original languageEnglish
Pages (from-to)1760-1774
Number of pages15
JournalEuropean Journal of Neuroscience
Volume28
Issue number9
DOIs
Publication statusPublished - Nov 1 2008

Keywords

  • Circadian rhythm
  • GABAergic neurons
  • Glutamatergic terminals
  • VIP neurons
  • Vasopressin-containing neurons

ASJC Scopus subject areas

  • Neuroscience(all)

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