Opioid-dopamine interaction in planaria: A behavioral study

Francesca Passarelli, Angelo Merante, Francesco E. Pontieri, Vito Margotta, Giorgio Venturini, Guido Palladini

Research output: Contribution to journalArticlepeer-review


The behavioral response of planaria to the exposure to selective opioid agonists was studied. The μ agonist [d-ala2, N-methyl-Phe4,Gly5-ol]enkephalin (DAMGO) and the δ agonist [D-Pen2, D-Pen5]enkephalin (DPDPE) failed to alter motor activity at all doses tested. Low doses of the selective κ agonist (±)-trans-U-50-trans-3,4-dichloro-N-methyl-N[2-(1-pyrrodinyl)-cyclohexyl]benzene acetamide methasulphonate (U50, 488) and bremazocine-HCl increased motor activity leading to C-like position (CLP) and screw-like hyperkinesia (SLH). These changes were identical to those seen previously with the exposure to D2 or D1 dopamine receptor agonists, respectively. Higher doses of κ agonists produced the enhancement of CLP and SLH together with robust snake-like movements (SLM). This latter response, that was typical of stimulation of κ opioid receptors, was blocked by co-exposure to naloxone or the selective κ antagonist Nor-binaltorphimine (Nor-BNI). Finally, co-exposure to sulpiride or SH-23390 respectively blocked the CLP or SLH response produced by U50,488 or bremazocine. Our data indicate the presence of κ opioid receptors in planaria and suggest the functional interaction between the opioid and dopamine system in this simple animal model. Copyright (C) 1999 Elsevier Science Inc.

Original languageEnglish
Pages (from-to)51-55
Number of pages5
JournalComparative Biochemistry and Physiology - C Pharmacology Toxicology and Endocrinology
Issue number1
Publication statusPublished - Sept 1999


  • Behavior
  • Bremazocine
  • Dopamine
  • Nor-BNI
  • Opioids
  • Planaria
  • Receptors
  • U50,488

ASJC Scopus subject areas

  • Immunology
  • Pharmacology


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