title: Antidepressant-like effect of endomorphin-1 and endomorphin-2 in mice.
abstract: Endomorphin-1 (Tyr-Pro-Trp-Phe-NH(2)) and endomorphin-2 (Tyr-Pro-Phe-Phe-NH(2)) are two recently isolated mu-opioid selective peptides with a potent antinociceptive activity, involved in a number of physiological processes, including food intake, vasomotricity, sexual behavior, as well as neuroendocrine and cardiorespiratory functions. The neuroanatomical distribution of endomorphins prompted us to study their antidepressant activity in two animal behavioral models of depression: forced-swimming and tail-suspension tests. In both tests, the intracerebroventricular (i.c.v.) injection of either endomorphin-1 or endomorphin-2 significantly decreased the duration of immobility, interpreted as an expression of 'behavioral despair', which could be related to the depression syndrome. These effects of endomorphins did not result from the stimulation of the animal motor activity. We have also demonstrated that the antidepressant-like effect of endomorphins was antagonized by the universal opioid antagonist, naloxone and the mu-opioid receptor selective antagonist, beta-funaltrexamine. In contrast, this effect was not antagonized by delta- and kappa-opioid receptor selective antagonists, naltrindole and nor-binaltorphimine, respectively. The results of the present study demonstrate that endomorphin-1 and endomorphin-2 produce potent antidepressant-like effects after i.c.v. injection in mice. We may suggest that endomorphins and the mu-opioid receptors might be involved in the physiopathology of depressive disorders, and that the endomorphinergic system could serve as a novel target for the development of antidepressant drugs.
authors.affiliation: Laboratory of Biomolecular Chemistry, Medical University of Lodz, Lodz, Poland.
authors.forename: Jakub
authors.initials: J
authors.lastname: Fichna
authors.forename: Anna
authors.initials: A
authors.lastname: Janecka
authors.forename: Mariola
authors.initials: M
authors.lastname: Piestrzeniewicz
authors.forename: Jean
authors.initials: J
authors.lastname: Costentin
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: do Rego
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000928:Antidepressive Agents / Q000627:therapeutic use*; D001522:Behavior, Animal / Q000187:drug effects*; D003863:Depression / Q000188:drug therapy*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D046352:Freezing Reaction, Cataleptic / Q000187:drug effects; D019417:Hindlimb Suspension / Q000379:methods; D008297:Male; D051379:Mice; D009043:Motor Activity / Q000187:drug effects; D009842:Oligopeptides / Q000627:therapeutic use*; D013550:Swimming; D013997:Time Factors
chemical_list: D000928:Antidepressive Agents; D009842:Oligopeptides; C105293:endomorphin 1; C105294:endomorphin 2