The effect of endomorphins on the release of 3H-norepinephrine from rat nucleus tractus solitarii slices

Mahmoud Al-Khrasani, Guy Elor, Mamode Yusuf Abbas, András Z. Rónai

Research output: Contribution to journalArticle

12 Citations (Scopus)


We used two, 3-min field stimulation cycles 30 min apart (S1, S2) in 3H-norepinephrine-loaded, superfused rat nucleus tractus solitarii-dorsal motor vagal nucleus (NTS-DVN) slices. The stimulation-induced release was expressed as the area above the baseline. Drugs were introduced 12 min before S2 and drug actions were characterized in terms of alterations of S2/S1 ratios. The S2/S1 ratio was 1.047 (0.946-1.159, n=4, geometric mean and 95% confidence interval) in controls and 0.336 (0.230-0.490, n=3), 0.726 (0.590-0.892, n=4), 0.613 (0.594-0.683, n=4) and 0.665 (0.500-0.886, n=4) in the presence of 10-6 M clonidine, D-Ala2,MePhe4,Gly5-ol-enkephalin (DAMGO), endomorphin-1 (Tyr-Pro-Trp-Phe-NH2, EM-1) and -2 (Tyr-Pro-Phe-Phe-NH2, EM-2) [the latter two in the presence of 10-4 M diprotin A, an inhibitor of dipeptidyl-aminopeptidase IV (DAP-IV) enzyme]. The effect of DAMGO at 10-5 M was significantly higher than at 10-6 M, whereas the effect of endomorphins did not differ at the two concentration levels. Diprotin A potentiated only very modestly the action of endomorphins. These data (a) confirm the presence of functional μ-opioid receptors in the vagal complex, (b) render it likely that the enzymic degradation of endomorphins is not a highly effective process in brain slices and (c) may suggest that the apparent ceiling in the effect of endomorphins might be related to their partial agonist property.

Original languageEnglish
Pages (from-to)97-101
Number of pages5
JournalRegulatory Peptides
Issue number1-3
Publication statusPublished - Mar 28 2003


  • Clonidine
  • D-Ala,MePhe,Gly-ol-enkephalin (DAMGO)
  • Diprotin A
  • Endomorphin-1
  • Endomorphin-2

ASJC Scopus subject areas

  • Biochemistry
  • Physiology
  • Endocrinology
  • Clinical Biochemistry
  • Cellular and Molecular Neuroscience

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