Peripheral effects of methionine-enkephalin on inflammatory reactions and behavior in the rat

Vesna Vujić-Redžić, Mirjana Dimitrijević*, Stanislava Stanojević, Vesna Kovačević-Jovanović, Tatjana Miletić, Jelena Radulović

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Methionine-enkephalin (Met-Enk) induces notable alterations in immune and central nervous system functions. The present study was conducted in order to compare peripheral and central effects of Met-Enk on nonspecific immunity, open field behavior and pain perception in the rat. The results showed that 0.2 mg/kg of Met-Enk given intraperitoneally (i.p.) increased concanavalin A (Con-A)-induced paw edema and enhanced basal and phorbol (myristate acetate (PMA)-stimulated H2O2 production of peritoneal macrophages. Met-Enk-induced immunopotentiation was antagonized by anti-Met- Enk antibodies (anti-Met-Enk-Ig) and quaternary naltrexone (qNtx). Met-Enk injected i.p. produced an increase of horizontal and vertical locomotor activity in the open field that was reversed by i.p. administration of anti- Met-Enk-Ig and qNtx. The dose of 0.2 mg/kg of Met-Enk applied i.p. did not affect the number of writhes in the test of analgesia. Intracerebroventricular (i.c.v.) injection of Met-Enk, given in a dose that was previously shown to be immunostimulatory, enhanced only basal H2O2 production of peritoneal macrophages, and anti-Met-Enk-Ig antagonized this effect. Besides, i.c.v. treatment with anti-Met-Enk-Ig increased and decreased H2O2 production of peritoneal macrophages under basal and stimulated conditions, respectively. Met-Enk and anti-Met-Enk-Ig injected i.c.v. did not influence activity in the open field and pain sensitivity. Thus, the i.c.v. dose of Met-Enk that was sufficient to modulate immune functions did not influence behavior. It may be concluded that Met-Enk modulated non-specific immune responses and open field behavior by peripheral mechanisms. Copyright (C) 2000 S. Karger AG, Basel.

Original languageEnglish (US)
Pages (from-to)70-77
Number of pages8
Issue number2
StatePublished - Jan 1 2000


  • Anti-methionine-enkephalin antibodies
  • Behavior
  • HO release
  • Methionine-enkephalin
  • Paw edema
  • Peritoneal macrophages
  • Rat

ASJC Scopus subject areas

  • Immunology
  • Endocrinology
  • Neurology
  • Endocrine and Autonomic Systems


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