Effects of alpha-adrenoceptor agonists and antagonists in a maze-exploration model of 'fear'-motivated behaviour

Naunyn Schmiedebergs Arch Pharmacol. 1984 Aug;327(1):1-5. doi: 10.1007/BF00504983.


An elevated X-maze with alternating open and enclosed arms was investigated as a model for the study of fear-induced behaviour. As predicted, the anxiolytics diazepam and amylobarbitone increased, and the putative anxiogenics ACTH and picrotoxin decreased the proportion of open arm entries. The alpha 1-adrenoceptor agonists phenylephrine and ST587, and the alpha 2-adrenoceptor antagonists idazoxan, piperoxane, RS-21361 and yohimbine decreased relative open-arm entries, thus resembling the putative anxiogenics. On the other hand, azepexole, clonidine and guanabenz, agonists at alpha 2-adrenoceptors, and the alpha 1-adrenoceptor antagonists prazosin and thymoxamine, enhanced the proportion of open arm entries at low doses, suggesting anxiolytic-like properties. A paradoxical fall in open arm entries occurred with these agents at higher doses. These results provide further evidence for the involvement of noradrenergic systems in 'fear'-motivated behaviour.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenergic alpha-Agonists / pharmacology*
  • Adrenergic alpha-Antagonists / pharmacology*
  • Adrenocorticotropic Hormone / pharmacology
  • Amobarbital / pharmacology
  • Animals
  • Clonidine / pharmacology
  • Diazepam / pharmacology
  • Exploratory Behavior / drug effects*
  • Fear*
  • Male
  • Models, Psychological
  • Picrotoxin / pharmacology
  • Prazosin / pharmacology
  • Rats


  • Adrenergic alpha-Agonists
  • Adrenergic alpha-Antagonists
  • Picrotoxin
  • Adrenocorticotropic Hormone
  • Amobarbital
  • Clonidine
  • Diazepam
  • Prazosin