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Orexin axons in the rat ventral tegmental area synapse infrequently onto dopamine and γ‐aminobutyric acid neurons

Balcita‐Pedicino, Judith Joyce, Sesack, Susan R.·2007·Journal of Comparative Neurology

Abstract

Cells in the ventral tegmental area (VTA) facilitate motivated behaviors, and the activity of VTA neurons is regulated by dense projections from the lateral hypothalamic area (LHA). Orexin (Orx) neurons in the lateral and perifornical hypothalamus play important roles in arousal, feeding, and energy metabolism. Orx cells contribute substantially to the LHA projection to the rat midbrain. However, the morphological features of Orx fibers in the VTA and whether they synapse onto dopamine (DA) or γ‐aminobutyric acid (GABA) neurons have not yet been investigated. We utilized immunoperoxidase and immunogold‐silver staining to examine the morphological features and synaptic incidence of Orx‐labeled axons in the VTA. We then combined immunoperoxidase labeling for Orx with immunogold‐silver labeling for GABA or for tyrosine hydroxylase (TH) in DA neurons. Electron microscopic analysis revealed that most Orx‐labeled axons in the VTA were passing fibers. The less common Orx varicosities were occasionally apposed to TH‐ or GABA‐labeled dendrites without synapsing. Only a small proportion of Orx‐positive axons synapsed onto dendrites or soma. The synapses included both asymmetric and symmetric types and targeted TH‐ and GABA‐labeled profiles with equal frequency. These findings suggest that most Orx fibers in the VTA are axons passing to caudal brainstem structures. However, Orx does mediate some direct synaptic influence on VTA DA and GABA neurons. Additional nonsynaptic effects are suggested by the presence of numerous dense‐cored vesicles. These studies have important implications for understanding the mechanisms whereby Orx can alter behavior through regulating VTA DA and GABA cell activity. J. Comp. Neurol. 503:668–684, 2007. © 2007 Wiley‐Liss, Inc.

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Crossref · 10.1002/cne.21420

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  • The nucleus accumbens shell is part of a neural loop including the lateral hypothalamus and the ventral tegmental area, with orexin neurons playing a key role.

    “The nucleus accumbens shell is thereby part of a neural loop including the lateral hypothalamus and the ventral tegmental area, with orexin neurons playing a key role ([7](#B7), [22](#B22), [77](#B77), [98](#B98), [115](#B115), [125](#B125), [175](#B175), [199](#B199)).”

    From Food reward, hyperphagia, and obesity (2011) · cites this paper as [7]

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Authors
Balcita‐Pedicino, J. J., & Sesack, S. R.
Affiliations
University of Pittsburgh (US)
Corresponding author
Sesack, Susan R.
Venue
Journal of Comparative Neurology
Publisher
Wiley
Published
2007-06-08
Volume
503
Issue
5
Pages
668-684
ISSN
  • 0021-9967 (ISSN-L)
  • 1096-9861
OpenAlex
W2044786960
Cited by
150
References
101
Citations by year
2026: 3 · 2025: 1 · 2024: 7 · 2023: 3 · 2022: 8 · 2021: 2 · 2020: 4 · 2019: 7 · 2018: 4 · 2017: 9 · 2016: 10 · 2015: 10 · 2014: 13 · 2013: 9 · 2012: 14
FWCI
5.50
Type
journal article
Language
en
Open access
closed
Locations
  • The Journal of Comparative Neurology (publishedVersion)
  • PubMed (publishedVersion)
Funders
National Institute of Mental Health (MH067937, R01MH067937)
Topics
  • Life Sciences › Neuroscience › Cognitive Neuroscience › Sleep and Wakefulness Research
  • Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Neurotransmitter Receptor Influence on Behavior
  • Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Neuroscience and Neuropharmacology Research
Keywords
orexin, ventral tegmental area, dopaminergic neurons, GABAergic neurons, varicose axons, tyrosine hydroxylase, lateral hypothalamus, midbrain projections, dense core vesicles
MeSH terms
Orexins, Animals, Axons, Dopamine, gamma-Aminobutyric Acid, Male, Neurons, Neuropeptides, Synapses, Ultrasonography, Microscopy, Immunoelectron, Silver Staining, Rats, Sprague-Dawley, Ventral Tegmental Area, Intracellular Signaling Peptides and Proteins, Rats

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