LY 171555-induced hyperdefensiveness in the mouse does not implicate benzodiazepine receptors

Catherine Belzung, Simona Cabib, Luigi Fabiani, Pietro Tolentino, Stefano Puglisi-Allegra

Research output: Contribution to journalArticle


In naive mice the selective D2 agonist LY171555 dose-dependently (0.5-5 mg/kg) induces defensive responses toward non-aggressive conspecifics. In order to investigate possible anxiogenic properties of the D2 agonist, its behavioural effects were compared with those produced by the benzodiazepine receptor inverse agonist methyl-β-carboline-3-carboxylate(β-CCM) in the elevated plus maze and in social interactions with non-aggressive opponents. When tested in the elevated plus maze, mice injected with LY 171555 (0.005-1 mg/kg) showed no decrease either of the number of entries or of the time spent in the open arms. At 5 mg/kg an actual increase of these two measures was observed. By contrast, β-CCM (1-3 mg/kg) dose-dependently decreased both the number of entries and the time spent in the open arms without altering locomotion. The effects of β-CCM were antagonized by the benzodiazepine receptor antagonist RO 15-1788 (3 mg/kg) showing a selective involvement of benzodiazepine receptors in their modulation. On the other hand, β-CCM, (1-3 mg/kg) did not produce significant effects on defensive behaviour of mice interacting with non-aggressive opponents and the defensive responses of mice treated with 1 mg/kg LY 171555 were not prevented by 5 mg/kg chlordiazepoxide. These results show that DA D2-mediated hyperdefensiveness and anxiety modulated by benzodiazepine receptors are unrelated phenomena and suggest that this behavioural response may represent a model of those forms of fear-related reaction that do not respond to benzodiazepine treatment.

Original languageEnglish
Pages (from-to)449-454
Number of pages6
Issue number4
Publication statusPublished - Apr 1991


  • Anxiety
  • D2 dopamine receptors
  • Defence
  • Plus maze test
  • Social interaction

ASJC Scopus subject areas

  • Pharmacology

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