Antinociceptive and gastrointestinal effects of opiates: an analysis of the nature of the involvement of mu and delta receptors of the central nervous system in morphine-tolerant and non-tolerant mice

Subbiah P. Sivam, Ing K. Ho

Research output: Contribution to journalArticle

2 Scopus citations


This study attempted to distinguish between μ (morphine) and δ [(D-Ala2-D-Leu5)-enkephalin; DADLE] receptors, with regard to both in vivo effects (analgesia and gastrointestinal motility) and the location of binding activity in the brain. Analgesia and motility are distinguishable both by dose (intracere-broventricular) and by ligand selectivity with μ ligands more potent for the former and δ for the latter. Tolerance and cross-tolerance are exhibited for both effects, with the relationships between μ and δ ligand potencies preserved. In vitro receptor binding revealed an affinity decrease for δ in medulla and an increase in medulla and diencephalon for μ receptors after tolerance development to morphine. The results indicate that the μ receptors in medulla and diencephalon mediate analgesia, while medullary δ receptors control motility.

Original languageEnglish (US)
Pages (from-to)105-108
Number of pages4
Issue number1
StatePublished - Jan 1984


ASJC Scopus subject areas

  • Pharmacology
  • Cellular and Molecular Neuroscience

Cite this