Multiple substrates for serotonergic modulation of rat locus coeruleus neurons and relationships with kainate receptors

Multiple substrates for serotonergic modulation of rat locus coeruleus neurons and relationships... The ultrastructural substrates of serotonin (5-hydroxytryptamine (5-HT)) immunoreactive terminals with respect to noradrenergic neurons of the locus coeruleus (LC) have only been suggested from immunocytochemical analysis in adjacent tissue sections using antisera directed against tryptophan and tyrosine hydroxylase (TH) enzymes. Here, we conducted dual immunoelectron microscopy in the same section of tissue using antisera directed against 5-HT and TH to determine cellular substrates for proposed interactions between these two transmitter systems. Axon terminals containing peroxidase labeling for 5-HT possessed small clear as well as large dense core vesicles. Of 176 5-HT-labeled axons and terminals, 19% contacted TH-labeled dendrites. When a synaptic specialization was detectable, it was more often of the asymmetric type. Electrophysiological studies have also shown that 5-HT selectively attenuates excitatory amino acid-induced activation of neurons in the LC. Thus, to further examine the cellular relationship between 5-HT-labeled axon terminals and excitatory amino acid receptors, we conducted immunogold-silver labeling of an antibody which recognized the three identified members of the kainate receptor (KAr) subunit class (GluR 5,6,7) and peroxidase localization of 5-HT. Similar proportions of 5-HT-labeled terminals (9%) were either apposed to KAr-labeled dendrites or exhibited KAr immunoreactivity. Twenty-four percent of the 5-HT axon terminals examined were apposed by glial processes that contained KAr. These data indicate that 5-HT axon terminals are in direct contact with LC neurons and also suggest pre- and postsynaptic sites for modulation of 5-HT terminals by excitatory amino acid ligands as well as indirect sites via glial processes. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Brain Research Bulletin Elsevier

Multiple substrates for serotonergic modulation of rat locus coeruleus neurons and relationships with kainate receptors

Brain Research Bulletin, Volume 51 (5) – Apr 1, 2000

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Publisher
Elsevier
Copyright
Copyright © 2000 Elsevier Science Inc.
ISSN
0361-9230
eISSN
1873-2747
DOI
10.1016/S0361-9230(99)00267-1
Publisher site
See Article on Publisher Site

Abstract

The ultrastructural substrates of serotonin (5-hydroxytryptamine (5-HT)) immunoreactive terminals with respect to noradrenergic neurons of the locus coeruleus (LC) have only been suggested from immunocytochemical analysis in adjacent tissue sections using antisera directed against tryptophan and tyrosine hydroxylase (TH) enzymes. Here, we conducted dual immunoelectron microscopy in the same section of tissue using antisera directed against 5-HT and TH to determine cellular substrates for proposed interactions between these two transmitter systems. Axon terminals containing peroxidase labeling for 5-HT possessed small clear as well as large dense core vesicles. Of 176 5-HT-labeled axons and terminals, 19% contacted TH-labeled dendrites. When a synaptic specialization was detectable, it was more often of the asymmetric type. Electrophysiological studies have also shown that 5-HT selectively attenuates excitatory amino acid-induced activation of neurons in the LC. Thus, to further examine the cellular relationship between 5-HT-labeled axon terminals and excitatory amino acid receptors, we conducted immunogold-silver labeling of an antibody which recognized the three identified members of the kainate receptor (KAr) subunit class (GluR 5,6,7) and peroxidase localization of 5-HT. Similar proportions of 5-HT-labeled terminals (9%) were either apposed to KAr-labeled dendrites or exhibited KAr immunoreactivity. Twenty-four percent of the 5-HT axon terminals examined were apposed by glial processes that contained KAr. These data indicate that 5-HT axon terminals are in direct contact with LC neurons and also suggest pre- and postsynaptic sites for modulation of 5-HT terminals by excitatory amino acid ligands as well as indirect sites via glial processes.

Journal

Brain Research BulletinElsevier

Published: Apr 1, 2000

References

  • Isolation and characterization of postsynaptic densities from various brain regions
    Carlin, R.K.; Grab, D.J.; Cohen, R.S.; Siekevitz, P.
  • Serotonin differentially modulates responses mediated by specific excitatory amino acid receptors in the rat locus coeruleus
    Charlety, P.J.; Chergui, K.; Akaoka, H.; Saunier, C.F.; Buda, M.; Aston-Jones, G.; Chouvet, G.
  • Spinal pathways mediating tonic, coeruleospinal, and raphe-spinal descending inhibition in the rat
    Jones, S.L.; Gebhart, G.F.
  • Serotonin-containing terminals synapse on septohippocampal neurons in the rat
    Milner, T.A.; Veznedaroglu, E.
  • Serotonergic innervation of the locus coeruleus from the dorsal raphe and its action on responses to noxious stimuli
    Segal, M.
  • Input from central nucleus of the amygdala efferents to pericoerulear dendrites, some of which contain tyrosine hydroxylase immunoreactivity
    Van Bockstaele, E.J.; Chan, J.; Pickel, V.M.

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