Actions of endomorphins on synaptic transmission of Aδ-fibers in spinal cord dorsal horn neurons

Yoichi Yajiri, Li Yen Mae Huang

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


The effects of endogenous μ-opioid ligands, endomorphins, on Aδ- afferent-evoked excitatory postsynaptic currents (EPSCs) were studied in substantia gelatinosa neurons in spinal cord slices. Under voltage-clamp conditions, endomorphins blocked the evoked EPSCs in a dose-dependent manner. To determine if the block resulted from changes in transmitter release from glutamatergic synaptic terminals, the opioid actions on miniature excitatory postsynaptic currents (mEPSCs) were examined. Endomorphins (1 μM) reduced the frequency but not the amplitude of mEPSCs, suggesting that endomorphins directly act on presynaptic terminals. The effects of endomorphins on the unitary (quantal) properties of the evoked EPSCs were also studied. Endomorphins reduced unitary content without significantly changing unitary amplitude. These results suggest that in addition to presynaptic actions on interneurons, endomorphins also inhibit evoked EPSCs by reducing transmitter release from Aδ-afferent terminals. Copyright (C) 2000 National Science Council.

Original languageEnglish (US)
Pages (from-to)226-231
Number of pages6
JournalJournal of Biomedical Science
Issue number3
StatePublished - 2000


  • Dorsal horn
  • Endomorphin
  • Nociceptive neurons
  • Spinal cord
  • Substantia gelatinosa
  • μ-Opioid

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Molecular Biology
  • Clinical Biochemistry
  • Cell Biology
  • Biochemistry, medical
  • Pharmacology (medical)


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