LY 171555-induced hyperdefensiveness in the mouse does not implicate benzodiazepine receptors. Belzung, C., Cabib, S., Fabiani, L., Tolentino, P., & Puglisi-Allegra, S. Psychopharmacology, 103(4):449--454, 1991.
abstract   bibtex   
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-beta-carboline-3-carboxylate(beta-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, beta-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 beta-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, beta-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.
@article{ belzung_ly_1991,
  title = {{LY} 171555-induced hyperdefensiveness in the mouse does not implicate benzodiazepine receptors},
  volume = {103},
  issn = {0033-3158},
  abstract = {In naive mice the selective D2 agonist {LY}171555 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-beta-carboline-3-carboxylate(beta-{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, beta-{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 beta-{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, beta-{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.},
  language = {eng},
  number = {4},
  journal = {Psychopharmacology},
  author = {Belzung, C. and Cabib, S. and Fabiani, L. and Tolentino, P. and Puglisi-Allegra, S.},
  year = {1991},
  pmid = {1676525},
  keywords = {Aggression, Animals, Behavior, Animal, Carbolines, Chlordiazepoxide, Convulsants, Dopamine Agents, Dose-Response Relationship, Drug, Ergolines, Flumazenil, Mice, Mice, Inbred C57BL, Quinpirole, Receptors, {GABA}-A, Social Behavior},
  pages = {449--454}
}

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