Synaptic connections of glutamatergic nerve fibres in the rat suprachiasmatic nucleus.
OBJECTIVE
The hypothalamic suprachiasmatic nucleus functioning as the principal circadian pacemaker in mammals, has a rich glutamatergic innervation. Nothing is known about the terminations of the glutamatergic fibres. The aim of the present investigations was to study the relationship between glutamatergic axon terminals and vasoactive intestinal polypeptide (VIP), GABA and arginine-vasopressin (AVP) neurons in the cell group.


METHODS
Double label immunocytochemistry was used and the brain sections were examined under the electron microscope. Vesicular glutamate transporter type 2 was applied as marker of the glutamatergic elements. Results - Glutamatergic fibers were detected in synaptic contact with GABAergic, VIP- and AVP-positive neurons forming asymmetric type of synapses.


CONCLUSIONS
The findings are the first data on the synaptic contacts of glutamatergic axon terminals with neurochemically identified neurons in the suprachiasmatic nucleus.
Kiss
József
J
Neuromorphological and Neuroendocrine Research Laboratory, Hungarian Academy of Sciences and Semmelweis University, Budapest.
Csáki
Agnes
A
Csaba
Zsolt
Z
Halász
Béla
B
D000818:Animals; D001120:Arginine / Q000378:metabolism; D001369:Axons / Q000502:physiology; D015415:Biomarkers / Q000032:analysis; D002940:Circadian Rhythm; D018698:Glutamic Acid / Q000378:metabolism*; D007150:Immunohistochemistry / Q000379:methods; D008854:Microscopy, Electron; D009412:Nerve Fibers / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D013493:Suprachiasmatic Nucleus / Q000378:metabolism / Q000502:physiology*; D013569:Synapses / Q000502:physiology*; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism; D014667:Vasopressins / Q000378:metabolism; D050599:Vesicular Glutamate Transport Protein 2 / Q000032:analysis; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D015415:Biomarkers; D050599:Vesicular Glutamate Transport Protein 2; D014667:Vasopressins; D014660:Vasoactive Intestinal Peptide; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D001120:Arginine