Immunoreactivity for endomorphin-2 occurs in primary afferents in rats and monkey

Tracie L. Pierce, Michael D. Grahek, Martin W. Wessendorf

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113 Scopus citations


ANTISERA were raised against endomorphin-2, a recently isolated endogenous opioid peptide that binds potently and selectively to the μ- opioid receptor. When sections of spinal cord were stained immunocytochemically, a dense plexus of fibres and varicosities was visualized in the superficial dorsal horn of rats and one monkey. Following unilateral multiple dorsal rhizotomy, labeling for endomorphin-2 was markedly reduced ipsilateral to the lesion. In sections stained for both endomorphin- 2 and CGRP, double-labeling was observed. Taken together, these data suggest that endomorphin-2 occurs in small diameter primary afferent fibres in rodents and primates. It appears possible that the release of neurotransmitters from nociceptive primary afferents might be regulated by release of endomorphin-2 from primary afferent terminals.

Original languageEnglish (US)
Pages (from-to)385-389
Number of pages5
Issue number3
StatePublished - Feb 16 1998


  • CGRP
  • Endogenous opioid
  • Pain
  • Spinal cord
  • μ-opioid receptor


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