Endomorphin-2 axon terminals contact mu-opioid receptor-containing dendrites in trigeminal dorsal horn

Sue Aicher, Jennifer L. Mitchell, Kristin C. Swanson, James E. Zadina

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

The endomorphins represent a novel group of endogenous opioid peptides that have high affinity for the mu-opioid receptor (MOR1). Endomorphin-2 is present in high density in the spinal and trigeminal dorsal horns and is localized to primary afferents. If endomorphin-2 were an endogenous ligand for the MOR1, we would expect to find the receptor at cellular sites in close association with the peptide. We used dual-labeling immunocytochemical methods combined with electron microscopy to determine if a cellular substrate exists for functional interactions between endomorphin-2 and MOR1. We confirmed the localization of endomorphin-2 to unmyelinated axons and axon terminals in the trigeminal dorsal horn. A small proportion of these endomorphin-2 axons contained MOR1, but many of the dendritic targets of endomorphin-2 terminals contained MOR1. Consistent with previous studies, endomorphin-2 was contained primarily in dense core vesicles and MOR1 was located primarily at non-synaptic sites. These morphological characteristics are consistent with the hypothesis that peptides are released extra-synaptically and their receptors may be located at sites distal to the synaptic junction. These anatomical data support the hypothesis that endomorphin-2 is a ligand for MORs in the trigeminal dorsal horn, particularly at postsynaptic sites.

Original languageEnglish (US)
Pages (from-to)190-198
Number of pages9
JournalBrain Research
Volume977
Issue number2
DOIs
StatePublished - Jul 11 2003

Fingerprint

mu Opioid Receptor
Presynaptic Terminals
Dendrites
Axons
Ligands
Peptides
Opioid Peptides
endomorphin 2
Spinal Cord Dorsal Horn
Secretory Vesicles
Electron Microscopy

Keywords

  • Confocal microscopy
  • Electron microscopy
  • Endogenous opioid
  • Extrasynaptic receptor
  • Pain

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Endomorphin-2 axon terminals contact mu-opioid receptor-containing dendrites in trigeminal dorsal horn. / Aicher, Sue; Mitchell, Jennifer L.; Swanson, Kristin C.; Zadina, James E.

In: Brain Research, Vol. 977, No. 2, 11.07.2003, p. 190-198.

Research output: Contribution to journalArticle

Aicher, Sue ; Mitchell, Jennifer L. ; Swanson, Kristin C. ; Zadina, James E. / Endomorphin-2 axon terminals contact mu-opioid receptor-containing dendrites in trigeminal dorsal horn. In: Brain Research. 2003 ; Vol. 977, No. 2. pp. 190-198.
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